REXX: Version 1

This is the   $SUDOKU.REX   (REXX) program and is used to solve the Rosetta Code task of "sudoku".

This REXX program was originally written to assist in sudoku puzzle solving (by giving strong hints), and not to solve the puzzle outright.
The REXX program was written to give increasing better hints and also show the possibilities (of what is possible solution for any cell),
and to partially solve the puzzle using distinct strategies (separately or in combination).   One option is to solve the puzzle.

The help for the   $SUDOKU   REXX program is included here ──► Sudoku/REXX#REXX_Version_1_Help.
The   $SUDOKU.REX   REXX program makes use of   $ERR.REX   REXX program which is used to display error messages (via   $T.REX).
The   $ERR.REX   REXX program is included here ──► Sudoku/REXX#REXX_Version_1_Errors.
The   $SUDOKU.REX   REXX program makes use of   $T.REX   REXX program which is used to display text messages.
The   $T.REX   REXX program is included here ──► Sudoku/REXX#REXX_Version_1_Messages.
Some older REXXes don't have a   changestr   BIF, so one is included here ──► Sudoku/REXX#REXX_Version_1_CHANGESTR_function.
REXX programs not included are   $H   which shows help and other documentation. <lang rexx>/*REXX program displays, can give hints, and/or solve a sudoku puzzle. */ trace off parse arg ! if !all(arg()) then exit if !cms then address signal on halt signal on noValue signal on syntax

ops=! /*remove extraneous blanks.*/ numeric digits 20 combos=1 @.=' ' /*initialize grid to blanks*/ !.= /*nullify valid empty# list*/ @abc='abcdefghijklmnopqrstuvwxyz' @abcU=@abc upper @abcU colors=!cms | !pcrexx | !r4 | !roo /*Are colors supported ? */ clear=1 /*option: clear the screen.*/ highLight=0 /*option: highlight singles*/ pruneall=0 /*option: prune all. */ prunemats=0 /*option: prune matches. */ prunesing=0 /*option: prune singles. */ pruneexcl=0 /*option: prune exclusives.*/ pruneline=0 /*option: prune lines. */ pruneonly=0 /*option: prune onlys. */ simple=0 /*option: show simple boxes*/ showoneline=0 /*option: show grid as1line*/ showgrid=1 /*option: show the grid. */ showinfo=1 /*option: show informatiion*/ showposs=0 /*option: show possible val*/ showcomb=0 /*option: show combinations*/ showrow= /*option: SHOWPOSS for rowN*/ showcol= /*option: SHOWPOSS for colN*/ showbox= /*option: SHOWPOSS for boxN*/ showcell= /*option: SHOWPOSS cellRC */ short=0 solve=0 /*option: solve the puzzle.*/ sod=lower(translate(!fn,,'$')) /*name of the puzzle. */ tellinvalid=1 /*tell err msg if invalid X*/ tops= /*option: used for $T opts.*/

gridindents=3 /*# spaces grid is indented*/ gridindent=left(,gridindents) /*spaces indented for grid.*/ gridwidth=7 /*grid cell interior width.*/ gridbar='b3'x /*bar for the grid (cells).*/ gridlt='da'x /*grid cell left top. */ gridrt='bf'x /*grid cell right top. */ gridlb='c0'x /*grid cell left bottom. */ gridrb='d9'x /*grid cell right bottom. */ gridline='c4'x /*grid cell line (hyphen). */ gridlin=copies(gridline,gridwidth) /*grid cell total line. */ gridemp=left(,gridwidth) /*grid cell empty (spaces).*/ griddj='c2'x /*grid cell down junction.*/ griduj='c1'x /*grid cell up junction.*/ gridlj='c3'x /*grid cell left junction.*/ gridrj='b4'x /*grid cell right junction.*/ gridcross='c5'x /*grid cell cross junction.*/

 do  while ops\==                         /*parse any and all options*/
 parse var ops _1 2 1 _ . 1 _o ops
 upper _
   select
   when _==','                    then nop
   when _1=='.' & pos("=",_)\==0  then tops=tops _o
   when  abb('PUZzle')            then      /*do PUZZ (whole) placement*/
        do
        puzz=na()
        if length(puzz)>81  then call er 30,puzz 'PUZZLE 1───►81'
                        do j=1  for length(puzz)
                        q=substr(puzz,j,1)
                        if q=='.'  then iterate
                        call vern q,'PUZZLE_digit'
                        c=j//9
                        if c==0  then c=9
                        r=(j-1)%9 + 1
                        @.r.c=q
                        end   /*j*/
        end
   when _=='CELL' then                      /*do CELL (grid) placement.*/
        do
        rc=nai()
        if length(rc)\==2                   then call er 30,y 'CELL'rc 2
        y=na()
        if length(y)>1                      then call er 30,y 'CELL'rc 1
        r=left(rc,1)
        c=right(rc,1)
        call vern r,'CELLrow'
        call vern c,'CELLcolumn'
        call vern y,'CELLdigit'
        @.r.c=y
        end
   when  abb('COLumn')  then                /*do ROW (grid) placement. */
        do
        n=nai()
        y=na()
        call vern n,'column'
        ly=length(y)
        if ly>9  then call er 30,y 'column'n '1───>9'
                        do j=1  for ly
                        x=substr(y,j,1)
                        if x== | x=="_" | x=='*' | x=="."  then iterate
                        if \isInt(x)  then call er 92,x 'cell_for_column'n
                        @.j.n=x
                        end   /*j*/
        end
   when  abb('ROW')  then                   /*do ROW (grid) placement. */
        do
        n=nai()
        y=na()
        call vern n,'row'
        ly=length(y)
        if ly>9  then call er 30,y 'row'n '1───>9'
                        do j=1  for ly
                        x=substr(y,j,1)
                        if x== | x=="_" | x=='*' | x=="."  then iterate
                        if \isInt(x)  then call er 92,x 'cell_for_row_'n
                        @.n.j=x
                        end   /*j*/
        end
   when abbn('CLearscreen')        then clear=no()
   when abbn('HIGHLightsingles')   then highLight=no()
   when abbn('PRUNEALL')           then pruneall=no()
   when abbn('PRUNEONLYs')         then pruneonly=no()
   when abbn('PRUNEEXclusives')    then pruneexcl=no()
   when abbn('PRUNELINEs')         then pruneline=no()
   when abbn('PRUNEMATches')       then prunemats=no()
   when abbn('PRUNESINGles')       then prunesing=no()
   when abbn('SIMPle')             then simple=no()
   when  abb('SHOWBOXes')|,
         abb('SHOWBOXs')           then showbox=nai()
   when  abb('SHOWCELLs')          then showcell=translate(na(),,',')
   when  abb('SHOWCOLs')           then showcol=nai()
   when abbn('SHOWCOMBinations')   then showcomb=no()
   when abbn('SHOWGrid')           then showgrid=no()
   when abbn('SHOWINFOrmation')    then showinfo=no()
   when abbn('SHOWONELINE')        then showoneline=no()
   when abbn('SHOWPOSSibles') then showposs=no()
   when  abb('SHOWROWs')           then showrow=nai()
   when abbn('SHortgrid')          then short=no()
   when abbn('SOLvepuzzle')        then solve=no()
   otherwise                       call er 55,_o
   end   /*select*/
 end     /*while ops¬==*/

if solve then pruneall=1 /*if solving, use PRUNEALL.*/

if pruneall then do /*if pruneAll, set ON other*/

                 pruneexcl=1
                 pruneonly=1
                 pruneline=1
                 prunemats=1
                 prunesing=1
                 end

aprune = , /*is there a PRUNExxx on ? */

                 pruneexcl |,
                 pruneonly |,
                 pruneline |,
                 prunemats |,
                 prunesing

if highLight then do /*HIGHLIGHTSINGLES opt on? */

                  hLl='-'
                  hLr='-'
                  if colors  then do
                                  hLl='('
                                  hLr=')'
                                  tops='.H=yell' tops
                                  end
                  end

tops=space(tops) box.=

 do j=1  for 9                              /*build the box bounds.    */
 rr=(((j*3)%10)+1)*3-2                      /*compute row lower bound. */
 cc=(((j-1)//3)+1)*3-2                      /*compute col lower bound. */
 boxr.j=rr
 boxc.j=cc
                       do   r=rr  to rr+2   /*build boxes with cell #s.*/
                         do c=cc  to cc+2
                         rc=r || c
                         box.j=box.j rc
                         box.rc=j
                         end   /*c*/
                       end     /*r*/
 box.j=strip(box.j)
 end   /*j*/

rowlb.=10 /*row R, low box number=b.*/ collb.=10 /*col R, low box number=b.*/ boxlr.=10 /*box B, low row number=r.*/ boxlc.=10 /*box B, low col number=c.*/

 do   r=1  for 9
   do c=1  for 9
   rc=r || c
   b=box.rc                                 /*what box is this R,C in ?*/
   rowlb.r=min(rowlb.r,b)                   /*find min box # for row R.*/
   collb.c=min(collb.c,b)                   /*find min box # for col C.*/
   boxlr.b=min(boxlr.b,r)                   /*find min row # for box B.*/
   boxlc.b=min(boxlc.b,c)                   /*find min col # for box B.*/
   end   /*c*/
 end     /*r*/
do j=1  to 9                                /*for each box, row, col...*/
rowhb.j=rowlb.j+2                           /*compute row's high box #.*/
colhb.j=collb.j+6                           /*compute col's high box #.*/
boxhr.j=boxlr.j+2                           /*compute box's high row #.*/
boxhc.j=boxlc.j+6                           /*compute box's high col #.*/
end   /*j*/

if showgrid then call showgrid 'the puzzle' /*show the grid to screen ?*/ if \validall() then exit /*validate specified digits*/ tellinvalid=0 /*don't tell err messages. */ !.= /*nullify valid empty# list*/ call buildposs /*build possible values. */ if showposs then call showgrid 'puzzle possibles' /*show 1st possibles?*/ if \validate(1) then exit /*validate the puzzle. */

if showoneline then do /*show grid as line line ? */

                    _=                      /*start with a clean slate.*/
                          do   r=1  for 9
                            do c=1  for 9
                            _=_ || @.r.c    /*build the string ...     */
                            end   /*c*/
                          end     /*r*/
                    _=translate(strip(_,'T'),".",' ')
                    if showinfo  then call $T 'one-line grid:'
                    call $T _
                    end

if aprune |,

  showposs then do
                call pruneposs              /*go build poss, then prune*/
                if showposs then call showgrid 'possibles' /*show grid.*/
                if \validate(1) then exit   /*validate the puzzle.     */
                end

if combos==1 then call $t sod 'puzzle solved.'

             else  if showcomb  then call $t 'combinations='comma(combos)

exit /*stick a fork in it, we're done.*/

/*─────────────────────────────vern subroutine──────────────────────────*/ vern: parse arg v,w /*verify a digit for an opt*/ if v== then call er 35,v w if \isInt(v) then call er 92,v w if v<1 | v>9 then call er 81,1 9 v w return

/*─────────────────────────────buildposs subroutine─────────────────────*/ buildposs: !.= /*nullify possibilities. */ combos=1

 do   rp=1  for 9                           /*build table of valid #s. */
   do cp=1  for 9                           /*step through each column.*/
   if @.rp.cp\==' '  then iterate           /*not blank?  Keep looking.*/
                         do jd=1  for 9     /*try each digit.          */
                         @.rp.cp=jd
                         if validx(rp,cp) then !.rp.cp=!.rp.cp || jd
                         end   /*jd*/
   combos=combos*length(!.rp.cp)            /*calculate # combinations.*/
   @.rp.cp=' '                              /*restore the point (blank)*/
   end      /*cp*/
 end        /*rp*/

return

/*─────────────────────────────showgrid subroutine──────────────────────*/ showgrid: parse arg title if clear then !cls /*clear the screen ? */ if title\== & showinfo then call $t !fn 'is showing' title gtail=copies3(gridlb || gridlin || copies2(griduj || gridlin) || gridrb) ghead=copies3(gridlt || gridlin || copies2(griddj || gridlin) || gridrt) call tg ghead gemp=copies3(copies3(gridbar || gridemp)gridbar) grid=copies3(gridlj || gridlin || copies2(gridcross || gridlin)gridrj) anyshow= \ ((showcell || showcol || showrow || showbox)\==)

 do jr=1  for 9
 if \short  then call tg gemp
 gnum=
   do jc=1  for 9
   _=@.jr.jc
   if _\==' ' & highLight  then _=hLl || _ || hLr
   if _==' ' & ,
      showposs  then do
                     jrjc=jr || jc
                     showit=anyshow
                     if showcell\== then if wordpos(jrjc,showcell)\==0 then showit=1
                     if showcol\==  then if pos(jc,showcol)\==0  then showit=1
                     if showrow\==  then if pos(jr,showrow)\==0  then showit=1
                            do jb=1  while  showbox\==
                            b=substr(showbox,jb,1)
                            if b==' '                   then leave
                            if wordpos(jrjc,box.b)\==0  then showit=1
                            end   /*jb*/
                     if showit  then _=strip(left(!.jr.jc,gridwidth),'T')
                     end
   gnum=gnum || gridbar || centre(_,gridwidth)
   if jc//3==0  then gnum=gnum || gridbar
   end   /*jc*/
 call tg gnum
 if \short  then call tg gemp
 if jr//3==0 then do
                  call tg gtail
                  if jr\==9  then call tg ghead
                  end
             else call tg grid
 end   /*jr*/

call $t return

/*─────────────────────────────validate subroutine──────────────────────*/ validate: /*are all empties possible?*/

 do   r=1  for 9                            /*step through each row.   */
   do c=1  for 9                            /*step through each column.*/
   if @.r.c==' ' & ,
      !.r.c==  then do                     /*no legal digit here.     */
                      if arg(1)==1  then call $t sod "puzzle isn't valid !"
                      return 0
                      end
   end   /*c*/
 end     /*r*/                              /*sub requires possibles.  */

return 1 /*indicate puzzle is valid.*/

/*─────────────────────────────validall subroutine──────────────────────*/ validall: /*validate all Q specified.*/

 do   r=1  for 9                            /*step through each row.   */
   do c=1  for 9                            /*step through each column.*/
   if @.r.c==' '  then iterate              /*if blank, then it's ok.  */
   y=                                       /*the rest of the row.     */
   rc=r||c
               do kc=1  for 9               /*compare to #s in column. */
               if kc\==c  then y=y|| @.r.kc /*build the rest of the row*/
               end   /*kc*/
   q=@.r.c
   if pos(q,y)\==0  then return tem(r,c,'row')    /*same # in same row?*/
   y=                                       /*the rest of the column.  */
               do kr=1  for 9               /*compare to #s in column. */
               if kr\==r then y=y || @.kr.c /*build the rest of the col*/
               end      /*kr*/
   if pos(q,y)\==0  then return tem(r,c,'col')    /*same # in same col?*/
   y=                                       /*the rest of the box.     */
   b=box.rc
     do   br=boxr.b  to boxr.b+2            /*compare to #s of the box.*/
       do bc=boxc.b  to boxc.b+2            /*build the rest of the box*/
       if br\==r & bc\==c  then y=y || @.br.bc
       end  /*bc*/
     end    /*br*/
   if pos(q,y)\==0  then return tem(r,c,'box')    /*same # in same box?*/
   end   /*c*/
 end     /*r*/

return 1 /*indicate all are valid.*/

/*─────────────────────────────validx subroutine────────────────────────*/ validx: arg r,c rc=r || c y= /*the rest of the row. */

          do kc=1  for 9                    /*compare to #s in column. */
          if kc\==c  then y=y || @.r.kc     /*build the rest of the row*/
          end   /*kc*/

q=@.r.c /*get the digit at r,c */ if pos(q,y)\==0 then return tem(r,c,'row') /*same number in same row ?*/ y= /*the rest of the column. */

     do kr=1  for 9                         /*compare to #s in column. */
     if kr\==r  then y=y || @.kr.c          /*build the rest of the col*/
     end   /*kr*/

if pos(q,y)\==0 then return tem(r,c,'col') /*same # in same column ?*/ y= /*the rest of the box. */ b=box.rc

          do   br=boxr.b  to boxr.b+2       /*compare to #s of the box.*/
            do bc=boxc.b  to boxc.b+2       /*build the rest of the box*/
            if br==r & bc==c  then iterate
            y=y || @.br.bc
            end   /*br*/
          end     /*bc*/

if pos(q,y)\==0 then return tem(r,c,'box') /*same # in same box ? */ return 1 /*indicate X (r,c) is valid*/

/*─────────────────────────────pruneposs subroutine─────────────────────*/ pruneposs: if \(prunesing | pruneexcl | prunemats | pruneline) then return call buildposs

 do prunes=1
 call $t !fn 'is starting prune pass #' prunes
 found=0                                    /*indicate no prunes so far*/
 if prunesing then do                       /*prune puzzle for singles.*/
                   _=prunesing()            /*find any singles ?       */
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if pruneexcl then do                       /*prune puzzle for singles.*/
                   _=pruneexcl()            /*find any excluives ?     */
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if pruneonly then do                       /*prune puzzle for onlys.  */
                   _=pruneonly()            /*find any onlys ?         */
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if prunemats then do jpm=2 to 8            /*prune puzzle for matches.*/
                   _=prunemats(jpm)         /*find any matches (len=j)?*/
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if pruneline then do                       /*prune puzzle for lines.  */
                   _=pruneline()            /*find 2 or more on a line?*/
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if \found then leave                       /*nothing found this time ?*/
 end    /*prunes*/

return

/*─────────────────────────────prunesing subroutine─────────────────────*/ prunesing: foundsing=0

   do   r=1  for 9
     do c=1  for 9
     _=length(!.r.c)                        /*get length of possible.  */
     if _==0   then iterate                 /*if null, then ignore it. */
     if _\==1  then iterate                 /*if not one digit, ignore.*/
     @.r.c=!.r.c                            /*it's 1 digit, a solution.*/
     !.r.c=                                 /*erase the old possible.  */
     foundsing=1
     call $t !fn 'found a single digit at cell' drc(r,c,@.r.c)
     end   /*c*/
   end     /*r*/

if foundsing then call buildposs /*re-build the possibles. */ return foundsing

/*─────────────────────────────pruneexcl subroutine─────────────────────*/ pruneexcl: foundexcl=0

 do exclusives=1                            /*keep building possibles. */
   do   r=1  for 9
     do c=1  for 9
     z=!.r.c
     lz=length(z)                           /*get length of possible.  */
     if lz==0  then iterate                 /*if null, then ignore it. */
     y=
     rc=r || c
     b=box.rc
               do   br=boxr.b  to boxr.b+2  /*compare to #s of the box.*/
                 do bc=boxc.b  to boxc.b+2  /*build the rest of the box*/
                 if br==r & bc==c  then iterate
                 y=y || @.br.bc || !.br.bc
                 end   /*bc*/
               end     /*br*/
                                            /*test for reduction.      */
      do t=1  for lz
      q=substr(z,t,1)
      if pos(q,y)==0 then do
                          foundexcl=1
                          @.r.c=q           /*it's a singularity, a sol*/
                          !.r.c=            /*erase old possibleity.   */
                          call $t !fn 'found the digit' q,
                                 "by exclusiveness at cell" drc(r,c,z)
                          call buildposs    /*re-build the possibles.  */
                          iterate exclusives
                          end
      end  /*t*/
     end   /*c*/
   end     /*r*/
 leave
 end       /*exclusives*/

return foundexcl

/*─────────────────────────────prunemats subroutine─────────────────────*/ prunemats: foundmatch=0 /*no matches found so far. */ parse arg L /*length of match, L=2,pair*/

 do matches=1
   do   r=1  for 9
     do c=1  for 9
     _=length(!.r.c)                        /*get length of possible.  */
     if _==0   then iterate                 /*if null, then ignore it. */
     if _\==L  then iterate                 /*not right length, ignore.*/
     qq=!.r.c
     m=0                                    /*count of matches so far. */
            do _c=1  for 9                  /*nother match in same row?*/
            if qq==!.r._c  then m=m+1       /*up count if it's a match.*/
            end  /*_c*/
     if m>=L then do pc=1  for 9            /*squish other possibles.  */
                  old=!.r.pc                /*save the "old" value.    */
                  if old==qq   then iterate /*if match, then ignore it.*/
                  if old==   then iterate /*if null poss, then ignore*/
                  new=squish(old,qq)        /*remove mat's digs from X.*/
                  if new==old  then iterate /*if no change,keep looking*/
                  !.r.pc=new                /*store new value into old.*/
                  foundmatch=1              /*indicate match was found.*/
                  call $t !fn 'is removing a'  old "from"  drc(r,pc,old),
                              'because of a match at'     drc(r,c,qq)
                  if length(new)==1 then do             /*reduce if L=1*/
                                         @.r.pc=new     /*store single.*/
                                         !.r.pc=        /*delete poss. */
                                         call buildposs /*re-build poss*/
                                         iterate matches  /*start over.*/
                                         end
                  end    /*pc*/
     m=0                                    /*count of matches so far. */
            do _r=1  for 9                  /*nother match in same col?*/
            if qq==!._r.c  then m=m+1       /*up count if it's a match.*/
            end   /*_r*/
     if m>=L then do pr=1  for 9            /*squish other possibles.  */
                  old=!.pr.c                /*save the "old" value.    */
                  if old==qq then iterate   /*if match, then ignore it.*/
                  if old== then iterate   /*if null poss, then ignore*/
                  new=squish(old,qq)        /*remove mat's digs from X.*/
                  if new==old then iterate  /*if no change,keep looking*/
                  !.pr.c=new                /*store new value into old.*/
                  foundmatch=1              /*indicate match was found.*/
                  call $t !fn 'is removing a'  old  "from" drc(pr,c,old),
                              'because of a match at' drc(r,c,qq)
                  if length(new)==1 then do             /*reduce if L=1*/
                                         @.pr.c=new     /*store single.*/
                                         !.pr.c=        /*delete poss. */
                                         call buildposs /*re-build poss*/
                                         iterate matches  /*start over.*/
                                         end
                  end   /*pr*/
     end                /*c*/
   end                  /*r*/
 leave
 end                    /*matches*/

return foundmatch

/*─────────────────────────────pruneonly subroutine─────────────────────*/ pruneonly: foundmatch=0 /*no matches found so far. */

 do findonlys=1                             /*keep searching ...       */
 _row.=                                     /*build str for each row . */
          do   r=1  for 9
            do c=1  for 9
            if !.r.c\==  then _row.r=_row.r !.r.c
            end   /*c*/
          end     /*r*/
 _col.=                                     /*build str for each boxcol*/
          do   c=1  for 9
            do r=1  for 9
            if !.r.c\==  then _col.c=_col.c !.r.c
            end   /*r*/
          end     /*c*/
   do   r=1  for 9
     do c=1  for 9
     q=!.r.c
     if q==  then iterate                 /*if empty, then ignore it.*/
       do j=1  to length(q)                 /*step through each digit. */
       k=substr(q,j,1)
       if kount1(k,_row.r) |,               /*is this the ONLY digit K?*/
          kount1(k,_col.c) then do i=1  to length(q)    /*prune others.*/
                                foundmatch=1
                                _=substr(q,i,1)
                                if _==k  then iterate   /*if=K, ignore.*/
                                o=squish(q,_)           /*remove others*/
                                !.r.c=o
                                call $t !fn  'removed part of an only',
                                             _   "from cell"   drc(r,c,q)
                                if length(o)==1  then   /*reduce if L=1*/
                                  do
                                  @.r.c=o               /*store single.*/
                                  !.r.c=                /*delete poss. */
                                  call buildposs        /*re-build poss*/
                                  iterate findonlys     /*start over.  */
                                  end
                                end   /*i*/
       end   /*j*/
     end     /*c*/
   end       /*r*/
 leave
 end     /*findonlys*/

return foundmatch

/*─────────────────────────────pruneline subroutine─────────────────────*/ pruneline: foundmatch=0 /*no matches found so far. */

do findlines=1                              /*keep searching ...       */
_boxr.=                                     /*build str for each boxrow*/
          do   r=1  for 9
            do c=1  for 9
            rc=r || c
            b=box.rc
            if !.r.c\==  then _boxr.r.b=strip(_boxr.r.b !.r.c)
            end   /*c*/
          end     /*r*/
 _boxc.=                                    /*build str for each boxcol*/
          do   c=1  for 9
            do r=1  for 9
            rc=r || c
            b=box.rc
            if !.r.c\==  then _boxc.c.b=strip(_boxc.c.b !.r.c)
            end   /*r*/
          end     /*c*/
 do r=1  for 9                              /*search all rows for twins*/
   do b=rowlb.r  to rowhb.r                 /*for each row, search box.*/
   aline=_boxr.r.b                          /*get a  row  in the box.  */
   if aline==  then iterate               /*if empty, ignore the line*/
   w=words(aline)                           /*W  is # of words in aline*/
   if w<2        then iterate               /*if < 2 words, ignore line*/
     do k=1  for 9                          /*search for each digit.   */
     f=pos(k,aline)                         /*pos of the 1st digit:  k */
     if f==0  then  iterate                 /*no dig k, so keep looking*/
     s=pos(k,aline,f+1)                     /*pos of the 2nd digit:  k */
     if s==0  then  iterate                 /*no 2nd k, so keep looking*/
       do jr=rowlb.r  to rowhb.r            /*look at the other 2 rows.*/
       if jr==r  then  iterate              /*if the same row, ignore. */
       if pos(k,_boxr.jr.b)\==0  then iterate k /*if no digit K, ignore*/
       end   /*jr*/
                                            /*found 2 Ks in row R box B*/
        do jb=rowlb.r  to rowhb.r           /*search boxes row R for K.*/
        if jb==b  then iterate              /*ignore if in the same box*/
        if pos(k,_boxr.r.jb)==0  then iterate
        foundmatch=1                        /*found a K in col C box JB*/
          do kc=1  for 9                    /*find which cell  K is in.*/
          rc=r || kc
          if box.rc==b        then iterate  /*ignore if in the same box*/
          _=!.r.kc
          if _==            then iterate  /*ignore if no possible.   */
          if pos(k,_)==0      then iterate  /*if no digit  K,  ignore. */
          call $t  !fn   'is row-line pruning digit' k,
                         'from cell'    drc(r,kc,!.r.kc)
          !.r.kc=squish(_,k)                /*remove mat's digs from X.*/
          if length(!.r.kc)==1  then do     /*pruned down to one digit?*/
                                     @.r.kc=!.r.kc  /*make a true digit*/
                                     !.r.kc=        /*erase possibility*/
                                     call buildposs /*rebuild possibles*/.
                                     iterate findlines
                                     end
          end   /*kc*/
        end     /*jb*/
     end        /*k*/
   end          /*b*/
 end            /*r*/
 do c=1  for 9                              /*search all cols for twins*/
   do b=collb.c  to colhb.c  by 3           /*for each col, search box.*/
   aline=_boxc.c.b                          /*get a  column in the box.*/
   if aline==  then iterate               /*if empty, ignore line*/
   w=words(aline)
   if w<2  then iterate                     /*if < 2 words, ignore line*/
     do k=1  for 9                          /*search for each digit.   */
     f=pos(k,aline)                         /*pos of the 1st digit:  k */
     if f==0  then iterate                  /*no dig k, so keep looking*/
     s=pos(k,aline,f+1)                     /*pos of the 2nd digit:  k */
     if s==0  then iterate                  /*no 2nd k, so keep looking*/
       do jc=boxlc.b  to boxhc.b            /*look at the other 2 cols.*/
       if jc==c  then iterate               /*if the same col, ignore. */
       if pos(k,_boxc.jc.b)\==0  then iterate k /*if no digit K, ignore*/
       end   /*jc*/
                                            /*found 2 Ks in col C box B*/
        do jb=collb.c  to colhb.c by 3      /*search boxes col C for K.*/
        if jb==b  then iterate              /*ignore if in the same box*/
        if pos(k,_boxc.c.jb)==0  then iterate
        foundmatch=1                        /*found a K in col C box JB*/
          do kr=1  for 9                    /*find which cell  K is in.*/
          rc=kr || c
          if box.rc==b       then iterate   /*ignore if in the same box*/
          _=!.kr.c
          if _==           then iterate   /*ignore if no possible.   */
          if pos(k,_)==0     then iterate   /*if no digit  K,  ignore. */
          call $t !fn  'is col-line pruning digit'  k,
                       'from cell'    drc(kr,c,!.kr.c)
          !.kr.c=squish(_,k)                /*remove mat's digs from X.*/
          if length(!.kr.c)==1  then do     /*pruned down to one digit?*/
                                     @.kr.c=!.kr.c  /*make a true digit*/
                                     !.kr.c=        /*erase possibility*/
                                     call buildposs /*rebuild possibles*/.
                                     iterate findlines
                                     end
          end   /*kr*/
        end     /*jb*/
     end        /*k*/
   end          /*b*/
 end            /*c*/
leave
end     /*findlines*/

return foundmatch

/*═════════════════════════════general 1-line subs════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════*/ !all:!!=!;!=space(!);upper !;call !fid;!nt=right(!var('OS'),2)=='NT';!cls=word('CLS VMFCLEAR CLRSCREEN',1+!cms+!tso*2);if arg(1)\==1 then return 0;if wordpos(!,'? ?SAMPLES ?AUTHOR ?FLOW')==0 then return 0;!call=']$H';call '$H' !fn !;!call=;return 1 !cal: if symbol('!CALL')\=="VAR" then !call=; return !call !env: !env='ENVIRONMENT'; if !sys=='MSDOS' | !brexx | !r4 | !roo then !env='SYSTEM'; if !os2 then !env='OS2'!env; !ebcdic=1=='f0'x; if !crx then !env='DOS'; return !fid: parse upper source !sys !fun !fid . 1 . . !fn !ft !fm .; call !sys; if !dos then do; _=lastpos('\',!fn); !fm=left(!fn,_); !fn=substr(!fn,_+1); parse var !fn !fn '.' !ft; end; return word(0 !fn !ft !fm,1+('0'arg(1))) !rex: parse upper version !ver !vernum !verdate .; !brexx='BY'==!vernum; !kexx='KEXX'==!ver; !pcrexx='REXX/PERSONAL'==!ver | 'REXX/PC'==!ver; !r4='REXX-R4'==!ver; !regina='REXX-REGINA'==left(!ver,11); !roo='REXX-ROO'==!ver; call !env; return !sys: !cms=!sys=='CMS'; !os2=!sys=='OS2'; !tso=!sys=='TSO' | !sys=='MVS'; !vse=!sys=='VSE'; !dos=pos('DOS',!sys)\==0 | pos('WIN',!sys)\==0 | !sys=='CMD'; !crx=left(!sys,6)=='DOSCRX'; call !rex; return !var: call !fid; if !kexx then return space(dosenv(arg(1))); return space(value(arg(1),,!env)) $fact!: procedure; parse arg x _ .; l=length(x); n=l-length(strip(x,'T',"!")); if n<=-n | _\== | arg()\==1 then return x; z=left(x,l-n); if z<0 | \isInt(z) then return x; return $fact(z,n) $fact: procedure; parse arg x _ .; arg ,n ! .; n=p(n 1); if \isInt(n) then n=0; if x<-n | \isInt(x) | n<1 | _ || !\== | arg()>2 then return x || copies("!",max(1,n)); !=1; s=x//n; if s==0 then s=n; do j=s to x by n; !=!*j; end; return ! $sfxa: parse arg ,s,m; arg u,c; if pos(left(s,2),u)\==0 then do j=length(s) to compare(s,c)-1 by -1; if right(u,j)\==left(c,j) then iterate; _=left(u,length(u)-j); if isNum(_) then return m*_; leave; end; return arg(1) $sfxf: parse arg y; if right(y,1)=='!' then y=$fact!(y); if \isNum(y) then y=$sfxz(); if isNum(y) then return y; return $sfxm(y) $sfxm: parse arg z; arg w; b=1000; if right(w,1)=='I' then do; z=shorten(z); w=z; upper w; b=1024; end; p=pos(right(w,1),'KMGTPEZYXWVU'); if p==0 then return arg(1); n=shorten(z); r=num(n,f,1); if isNum(r) then return r*b**p; return arg(1) $sfxz: return $sfxa($sfxa($sfxa($sfxa($sfxa($sfxa(y,'PAIRs',2),'DOZens',12),'SCore',20),'GREATGRoss',1728),'GRoss',144),'GOOGOLs',1e100) $t: if tops== then say arg(1); else do; !call=']$T'; call "$T" tops arg(1); !call=; end; return ab: arg ab,abl; return abbrev(ab,_,abl) abb: arg abbu; parse arg abb; return abbrev(abbu,_,abbl(abb)) abbl: return verify(arg(1)'a',@abc,'M')-1 abbn: parse arg abbn; return abb(abbn) | abb('NO'abbn) abn: arg ab,abl; return abbrev(ab,_,abl) | abbrev('NO'ab,_,abl+2) comma: procedure; parse arg _,c,p,t; c=pickBlank(c,","); o=p(p 3); p=abs(o); t=p(t 999999999); if \isInt(p) | \isInt(t) | p==0 | arg()>4 then return _; n=_'.9'; #=123456789; k=0; return comma_() comma_: if o<0 then do; b=verify(_,' '); if b==0 then return _; e=length(_)-verify(reverse(_),' ')+1; end; else do; b=verify(n,#,"M"); e=verify(n,#'0',,verify(n,#"0.",'M'))-p-1; end; do j=e to b by -p while k<t; _=insert(c,_,j); k=k+1; end; return _ copies2: return copies(arg(1),2) copies3: return copies(arg(1),3) drc: procedure; parse arg r,c,p; _=r","c; if p\== then _=_ "("p')'; return _ er: parse arg _1,_2; call '$ERR' "14"p(_1) p(word(_1,2) !fid(1)) _2; if _1<0 then return _1; exit result err: call er '-'arg(1),arg(2); return erx: call er '-'arg(1),arg(2); exit halt: call er .1 int: int=num(arg(1),arg(2)); if \isInt(int) then call er 92,arg(1) arg(2); return int/1 isInt: return datatype(arg(1),'W') isNum: return datatype(arg(1),'N') kount1: parse arg qd,string; k1=pos(qd,string); if k1==0 then return 0; return pos(qd,string,k1+1)==0 lower: return translate(arg(1),@abc,translate(@abc)) na: if arg(1)\== then call er 01,arg(2); parse var ops na ops; if na== then call er 35,_o; return na nai: return int(na(),_o) nail: return squish(int(translate(na(),0,','),_o)) nan: return num(na(),_o) no: if arg(1)\== then call er 01,arg(2); return left(_,2)\=='NO' noValue:!sigl=sigl; call er 17,!fid(2) !fid(3) !sigl condition('D') sourceline(!sigl) num: procedure; parse arg x .,f,q; if x== then return x; if isNum(x) then return x/1; x=space(translate(x,,','),0); if \isNum(x) then x=$sfxf(x); if isNum(x) then return x/1; if q==1 then return x; if q== then call er 53,x f; call erx 53,x f p: return word(arg(1),1) pickBlank: procedure; parse arg x,y; arg xu; if xu=='BLANK' then return ' '; return p(x y) shorten:procedure; parse arg a,n; return left(a,max(0,length(a)-p(n 1))) simple: return translate(arg(1),'.||--%<>AV'copies('+',25),"·│║─═☼◄►↑↓┤┐└┴┬├┼┘┌╔╗╚╝╟╢╞╡╫╪╤╧╥╨╠╣") squish: return space(translate(arg(1),,word(arg(2) ',',1)),0) syntax: !sigl=sigl; call er 13,!fid(2) !fid(3) !sigl !cal() condition('D') sourceline(!sigl) tem: parse arg r,c,w; if tellinvalid then say '***error!*** row' r", col" c '('@.r.c") is a duplicate of another in the same" w'.'; return 0 tg: arg tg; if simple then tg=simple(tg); call $t gridindent || tg; return</lang>

REXX Version 1 Output

output when using the input of:
row 1 .5..7.89 row 2 9...3 row 3 1...89.4 row 4 ..9.....1 row 5 ..13.52 row 6 6.....5 row 7 .6.89...3 row 8 ....5...7 row 9 .98.2..5 pruneALL

$SUDOKU is showing the puzzle
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │       │   5   │       ││       │   7   │       ││   8   │   9   │       │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   9   │       │       ││       │   3   │       ││       │       │       │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   1   │       │       ││       │   8   │   9   ││       │   4   │       │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │       │       │   9   ││       │       │       ││       │       │   1   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │       │       │   1   ││   3   │       │   5   ││   2   │       │       │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   6   │       │       ││       │       │       ││   5   │       │       │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │       │   6   │       ││   8   │   9   │       ││       │       │   3   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │       │       │       ││       │   5   │       ││       │       │   7   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │       │   9   │   8   ││       │   2   │       ││       │   5   │       │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘

$SUDOKU is starting prune pass # 1
$SUDOKU found the digit 8 by exclusiveness at cell 2,2 (2478)
$SUDOKU found the digit 3 by exclusiveness at cell 3,7 (367)
$SUDOKU found the digit 5 by exclusiveness at cell 4,1 (234578)
$SUDOKU found the digit 8 by exclusiveness at cell 5,1 (478)
$SUDOKU found the digit 9 by exclusiveness at cell 6,4 (12479)
$SUDOKU found the digit 9 by exclusiveness at cell 5,9 (469)
$SUDOKU found the digit 5 by exclusiveness at cell 7,3 (2457)
$SUDOKU found the digit 1 by exclusiveness at cell 8,2 (1234)
$SUDOKU found the digit 9 by exclusiveness at cell 8,7 (469)
$SUDOKU found the digit 8 by exclusiveness at cell 8,8 (268)
$SUDOKU found the digit 8 by exclusiveness at cell 6,9 (48)
$SUDOKU found the digit 8 by exclusiveness at cell 4,6 (24678)
$SUDOKU found the digit 4 by exclusiveness at cell 4,7 (467)
$SUDOKU found the digit 2 by exclusiveness at cell 7,8 (12)
$SUDOKU found the digit 4 by exclusiveness at cell 9,9 (46)
$SUDOKU found the digit 6 by exclusiveness at cell 9,7 (16)
$SUDOKU found the digit 1 by exclusiveness at cell 7,7 (1)
$SUDOKU found the digit 1 by exclusiveness at cell 2,8 (167)
$SUDOKU found the digit 7 by exclusiveness at cell 2,7 (7)
 ∙
 ∙
 ∙
   some output elided ∙∙∙
 ∙
 ∙
 ∙ 
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │   4   │   5   │   3   ││   1   │   7   │   6   ││   8   │   9   │   2   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   9   │   8   │   6   ││   4   │   3   │   2   ││   7   │   1   │   5   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   1   │   2   │   7   ││   5   │   8   │   9   ││   3   │   4   │   6   │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │   5   │   3   │   9   ││   2   │   6   │   8   ││   4   │   7   │   1   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   8   │   7   │   1   ││   3   │   4   │   5   ││   2   │   6   │   9   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   6   │   4   │   2   ││   9   │   1   │   7   ││   5   │   3   │   8   │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘
   ┌───────┬───────┬───────┐┌───────┬───────┬───────┐┌───────┬───────┬───────┐
   │       │       │       ││       │       │       ││       │       │       │
   │   7   │   6   │   5   ││   8   │   9   │   4   ││   1   │   2   │   3   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   2   │   1   │   4   ││   6   │   5   │   3   ││   9   │   8   │   7   │
   │       │       │       ││       │       │       ││       │       │       │
   ├───────┼───────┼───────┤├───────┼───────┼───────┤├───────┼───────┼───────┤
   │       │       │       ││       │       │       ││       │       │       │
   │   3   │   9   │   8   ││   7   │   2   │   1   ││   6   │   5   │   4   │
   │       │       │       ││       │       │       ││       │       │       │
   └───────┴───────┴───────┘└───────┴───────┴───────┘└───────┴───────┴───────┘

$SUDOKU is starting prune pass # 4
 sudoku puzzle solved.

REXX Version 1 Help

The following text file is the documentation (HELp) for the   $SUDOKU.REX   program.

Note that the   $SUDOKU#   ($SUDOKU#.REX)   isn't included here because of the size of the program.

The  $SUDOKU  command will display a sudoku puzzle, cells/rows/columns of which
may be specified.     A sudoku puzzle is a grid of nine 3x3 cells  (for a total
of 9x9 cells)  that can contain the digits 1──►9.    The object is to fill in
the puzzle so that every row, column,  and  3x3 box  has every (unique) digit.

To show several supplied sudoku puzzles, the  $SUDOKU#   program can be used to
display over 12,600 different puzzles.   To see that help, issue:   $H $SUDOKU#

╔══════════════════════════════════════════════════════════════════════════════╗
║                         {CLearscneen | NOCLearscreen}                        ║
║                         {HIGHLightsingles | NOHIGHLightsingles}              ║
║                         {PUZZle .d..dd..d.......d..dddd.ddd...ddd.dddd....}  ║
║                         {COLumn n .d..dd..d.}                                ║
║                         {ROW    n ...d..d.dd}                                ║
║  $SUDOKU                {CELL  rc d}                                         ║
║                         {PRUNEEXCLusives}   {PRUNELINEs}                     ║
║            ?            {PRUNEMATches}      {PRUNEONLYs}      {PRUNESINGLes} ║
║            ?AUTHOR      {PRUNEALL}                                           ║
║            ?FLOW        {SHORTgrid}                                          ║
║            ?SAMPLES     {SHOWCELL rc,xy,ab,...}                              ║
║                         {SHOWBOXes bbb}    {SHOWCOLs ccc}    {SHOWROWs rrr}  ║
║                         {SHOWCOMBinations}                                   ║
║                         {SHOWGrid | NOSHOWGrid}                              ║
║                         {SHOWINFOmation | NOSHOWINFOmation}                  ║
║                         {SHOWPOSSibles}                                      ║
║                         {SHOWONELINE}                                        ║
║                         {SIMPLE}                                             ║
║                         {tops}                                               ║
╚══════════════════════════════════════════════════════════════════════════════╝

───where:

?          shows this help file              (press  ESC  to quit when viewing).

?AUTHOR    shows the author of this program.

?FLOW      shows the external execution flow of this program.

?SAMPLES   shows some sample uses            (press  ESC  to quit when viewing).

CLearscreen     clears the screen before any grid is shown.
                                                    The default is:  CLEARSCREEN

NOCLearscreen   doen't clear the screen before any grid is show.
                                                    The default is:  CLEARSCREEN

HIGHLightsingles  highlights all specified digits  (if the grid is shown).
                  A highlighted digits is prefixed and suffixed with a
                  minus sign (-), or shown in yellow if running on CMS or
                  with PC/REXX.              The default is:  NOHIGHLIGHTSINGLES

NOHIGHLightsingles  doesn't highlight specified digits  (if the grid is
                    shown).                  The default is:  NOHIGHLIGHTSINGLES

PUZZle .d..dd..d.......d..dddd.ddd...ddd.dddd....    (for example)
                The character string that follows  are the digits  to be placed
                into the puzzle  (going from left to right).  row by row.   Any
                position  that has a  period (.)  is skipped over.    The  10th
                character would be the start of row 2, the 19th character would
                be the start of row 3, etc.  The character string is considered
                to "wrap around",  row to row.  Up to 81 chars may be specified.

COL n .d..dd..d.    (for example)
                D  is the column to be specified and must be  1 ───► 9.    The
                character string that follows  are the digits  to be placed  in
                that column  (going from top to bottom),  and any position that
                has a period (.) is skipped over.  I.E., to set  column 9  (the
                rightmost column) to    blank 3 blank blank 4 7 blank 8,    the
                following could be specified:   col 9 .3..47.8     (the rest of
                the column is left blank).   Up to 9 digits  (or chars)  may be
                specified.  Any number of   COL   keywords may be specified and
                they may be given in any order.

ROW n ...d..d.dd    (for example)
                D  is the  row   to be specified and must be  1 ───► 9.     The
                character string that follows  are the digits  to be placed  in
                that row (going from left to right),  and any position that has
                a period (.) is skipped over.     I.E.,  to set row 5      (the
                middle row) to      blank blank 6 9 blank 5 blank 2,        the
                following could be specified:    row 5 ..69.5.2       (the rest
                of the row is left blank).    Up to nine digits  (or chars) may
                be specified.   Any number of   ROW  keywords  may be specified
                and they may be given in any order.

CELL rc d       R  is the  row   to be specified and must be  1 ───► 9,
                C  is the  col   to be specified and must be  1 ───► 9,
                D  is the  digit to be  placed   and must be  1 ───► 9   or  "."

                I.E.,  to set the 4th cell in the grid (row 1, col 4)  to the
                digit 7, the following could be specified:   CELL 14 7
                Any number of  CELL  keywords my be specified and they may be
                in any order.

PRUNEEXCLusives will prune any possible values that are the only value (digit)
                for a box.  If  PRUNESINGLE  is in effect,  than this digit is
                made into a specified digit  (solves that cell).
                                              The default is:  NOPRUNEEXCLUSIVES

PRUNEMATches    will prune any possible values that are matched up (two pairs,
                three triplets, ...) and then removes them from any other
                possible on the same row and/or column.   If  PRUNESINGLE  is
                in effect, any possible values that have now become one digit
                are made into a specified digit.
                                                 The default is:  NOPRUNEMATCHES

PRUNEONLYs      will prune any possible values  that are the  only  digit  in a
                row or column,  and then then  removes all other digits in that
                cell, and if just a single digit remains,  makes it a specified
                digit (solves that cell).          The default is:  NOPRUNEONLYS

PRUNESINGles    will prune any possible values that have a single value (one
                digit) to be as if it were a specified digit.    This is the
                simplest form of pruning.        The default is:  NOPRUNESINGles

PRUNELINEs      will prune any possible values that exist in any row or column
                that can only can exist in a particular row or column in a
                box.                               The default is:  NOPRUNELINEs

PRUNEALL        will prune all of the above  PRUNExxx.
                                                     The default is:  NOPRUNEALL

SHORTgrid       shows a shortened versin of the grid.
                                                    The default is:  NOSHORTGRID

NOSHORTgrid     shows a   full    versin of the grid.
                                                    The default is:  NOSHORTGRID

SHOWBOXes bbb   when showing POSSibles,  only those boxes   (BBB...)  specified
                have their possible digits shown,  where  B  is the box
                number(s)   and must be  1 ───► 9.
                The boxes are numbered  left to right, top to bottom,  with the
                top left-most box is 1, the middle box is 5, and the 1st box in
                the middle row is box 4,  the 1st box on the last row is box 7.
                                                     The default is:  all boxes.

SHOWCOLs ccc    when showing POSSibles, only those columns  (CCC...)  specified
                have  their possible  digits  shown,  where   C   is the column
                number(s)   and must be  1 ───► 9.
                The columns are numbered left to right.
                                                    The default is:  all columns

SHOWROWs ccc    when showing POSSibles,   only those rows  (CCC...)  specified
                have their possible digits shown,   where    R    is the row
                number(s)   and must be  1 ───► 9.
                The rows are numbered top to bottom.
                                                       The default is:  all rows

SHOWCOMBinations    shows the number of combinations of all the possible
                    values.                  The default is:  NOSHOWCOMBinations

NOSHOWCOMBinations  doesn't show the number of combinations of all the
                    possible values.         The default is:  NOSHOWCOMBinations

SHOWGrid        shows the sudoku puzzle  in a grid  after  the digits are
                specified,  after  computing  the  possible values  (if wanted),
                after each pruning (if any).           The default is:  SHOWGrid

NOSHOWGrid      doesn't show the grid.                 The default is:  SHOWGrid

SHOWINFOmation    shows various information messages such as screen titles,
                  action being taken, etc.      The default is:  SHOWINFOrmation

NOSHOWINFOmation  doesn't show the informational messages.
                                                The default is:  SHOWINFOrmation

SHOWPOSSibles   shows what digits are possible for each empty cell.
                The   SHOWGrid   option  must be  ON,  and  the cells shown are
                restricted (if given) by   SHOWCELL,  SHOWCOLs,  and  SHOWROWs.
                                               The default is:  NOSHOWPOSSibles

SHORTgrid       shows a shortened versin of the grid.
                                                    The default is:  NOSHORTGRID

NOSHORTgrid     shows a   full    versin of the grid.
                                                    The default is:  NOSHORTGRID

SHOWONELINE     shows a the puzzle as speiified as line line of:
                ....dd....d.d.d..d.....d....d.dd...d.....d....d   (for example).
                Up to  81  characters  may be shown,  and  any trailing periods
                aren't shown.                     The default is:  NOSHOWONELINE

                +---+
SIMPle     uses |   | for the boxing characters.       The default is:  NOSIMPle
                +---+

                ┌───┐
NOSIMPle   uses │   │ for the boxing characters.       The default is:  NOSIMPle
                └───┘

tops       are any or all of the following  $T  .X=xxx options.


────────────────────────────────────────────────────────────────────────────────

Some (but not all) of the  $T  options are:   (issue    $T ?    for more help)

────────  ──────────────────────────────────────────────────────────────────────

.I=nnn    indents the messages   nnn   spaces,   the default is 0.

.C=color  sets the  color  of the messages,  there is no default.

.H=color  sets the highlight color of any parenthesized text,  there is
          no default.

.F=fff    writes the information (in addition to typing it) to the file,  fff
          there is no default.

                                       Ω

REXX Version 1 Errors

The   $ERR.REX   (REXX) program is used to issue various formatted error messages from other REXX programs.

The   $ERR.REX   program makes use of the   $T.REX   program to issue the error messages in red (if available).

The help for the   $ERR   REXX program is included here ──► $ERR.HEL. <lang rexx>/*REXX*/ trace off /*turn off all REXX cmd err msgs.*/ parse arg ! /*obtain the original arguments. */ if !all(arg()) then exit /*if a request for doc, then exit*/ if !cms then address /*handle ADDRESS for CMS. */ signal on halt /*setup label for HALT condition.*/ signal on noValue /* " " " NOVALUE " */ signal on syntax /* " " " SYNTAX " */ numeric digits 100 /*what the hell, support big 'uns*/

                                      /*══════list of external commands*/

@ctty = 'CTTY' /*point to the CTTY command.*/ @globalv = 'GLOBALV' /* " " " GLOBALV " */ @finis = 'FINIS' /* " " " FINIS " */ @subcom = 'SUBCOM' /* " " " SUBCOM " */ @cpset = 'CP SET' /* " " " CP SET " */ @conwait = 'CONWAIT' /* " " " CONWAIT " */ @cpspool = 'CP SPOOL' /* " " " CP SPOOL " */ @cmstype = 'SET CMSTYPE' /* " " " SET CMSTYPE " */

if !cms | !dos then @ = '────────' /*use hyphens for dashes in msgs*/

               else @ = '--------'    /* "   minuses  "     "    "   " */

parse var !! !! ' ..F=' ftops /*is $ERR to write errors to file*/ if ftops\== then ftops='.F='ftops /*Yes, then add to FTOPS var. */ etops=strip(ftops '.C=red .END=1') /*also, add to ETOPS variable. */ g.1=space(!!) /*a version with no extra blanks.*/ pblank='05'x /*use pseudoBlank as "true" blank*/

 do j=2  to 9                         /*process some possible shortcuts*/
 k=j-1                                /*point to the previous variable.*/
 parse var g.k a.k g.j                /*get the "G" version (= "all"). */
 if a.k==','  then a.k=               /*if omitted, then use a null.   */
 g.k=translate(g.k,,pblank)           /*translate to a true blank.     */
 a.k=translate(a.k,,pblank)           /*    "      " "   "    "        */
 aU.k=a.k;  upper aU.k                /*get an uppercase version of a.k*/
 L.k=length(a.k)                      /*get the length of the a.k  var.*/
 c.k=comma(a.k)                       /*add a comma (,) to the number. */
 w.k=length(c.k)                      /*get the length of commatized #.*/
 end   /*j*/
                                      /* [↓]  shortcut versions of  a. */

a2=a.2; a3=a.3; a4=a.4; a5=a.5; a6=a.6; a7=a.7; a8=a.8

          g3=g.3;    g4=g.4;    g5=g.5;    g6=g.6;    g7=g.7;    g8=g.8

aa5=a.5 if isNum(aa5) then aa5=abs(aa5) /*if it's a number, use ABS value*/ i=a.1 /*this is the error number. */ errmsgto= errmsgnt= xedit=0 /*indicate no XEDIT (so far). */

if !cms then do /*if CMS, then do some housework.*/

             @globalv 'SELECT' !fn 'GET ERRMSGTO ERRMSGNT'
             @finis '* * *'
             @cmstype 'RT'
             @conwait
             @cpspool 'CON TERM'
             @cpset' IMSG ON'
             @cpset' EMSG ON'
             @subcom 'XEDIT'
             xedit=\rc  &  \cmsflag('SUBSET')
             ufid=a3 a4 a5
             end

if !dos then do /*if COS, then do some housework.*/

             if \!nt  then @ctty 'con'  /*Not Windows NT?  Use CTTY cmd*/
             _=a4
             if _\==  &  right(_,1)\=="\"  then _=_'\'
             ufid=_ || a2"."a3
             end

i=space(translate(i,,'-'),0) /*remove all minus signs from str*/ if i== then call erb 57 /*Is it null? Oops-say message.*/

if i=0 then do /*if "error" is zero, show author*/

            _=                        /*start with a clean slate.      */
            iL=length(i)              /*use # of zeroes for more info. */
            if iL>1  then _=@'author'@"÷÷÷÷Gerard J. Schildberger"
            if iL>2  then _=_           '÷÷phone   (701)-242-8238'
            if iL>3  then _=_           '÷÷E-mail gerardS@rrt.net'
            if iL>5  then _=_           '÷÷9411  West Ridge Road,'
            if iL>5  then _=_           '÷÷Hankinson, ND    58041'
            atops=strip(ftops '.A=-2 .X=-2 .E=2 .C=yell .J=c .BOX= .KD=÷')
            if _\==  then call $t atops _  /*tell if more than 1 zero*/
            exit 0                    /*exit with a return code of zero*/
            end

if i==14000 |, /*is this a message for a HALT ? */

  i=='14.1'  then do                  /* ··· or in some cases,  14.1   */
                  htops=strip(ftops '.X=-1 .C=red .J=c .BOX=')
                  call $t htops 'The REXX program' @ a2 @ "has been halted !"
                  exit 14000          /* ··· and indicate a HALT cond· */
                  end


if \isInt(i) then call erb 53,i "error_code" /*Hmmm, an "internal" err*/ oi=i /*keep the original value around.*/ xedit= xedit & i>0 /*inside the XEDIT program? */ i=abs(i) /*use the absolute value of I. */ if i<1400 | i>1499 then call erb 99,oi /*check for a legal range of I. */ k=i-1400 /*from now on, use a shorter I. */ if xedit then address 'XEDIT' "SET MSGM ON LONG" /*allow XEDIT msgs.*/ call sy /*write blank line.*/ call sy "($$$"i") *error*:" /*write a hdr line.*/

if k==0 then call sy "some commands can't or shouldn't be executed while in" g3 if k==1 then call sy "the" g3 'was previously specified or specified more than once' if k==2 then call sy "the" a4 "argument can't be" choose("negative",g5)":" a3 if k==3 then call sy 'the (disk) filemode' a3 "can't have any read-only extensions" g4 if k==4 then call sy 'the' a4 "filemode/address can't be" choose('RELEASEd',g5)":" a3 if k==5 then do

             call sy "illegal compator operator" @ a3 'specified,'
             call sy "it must be one of:    =  \=  <  <=  >  >=  \<  \>"
             end

if k==6 then call sy "no special characters are allowed in the" g4':' a3 if k==7 then call sy "fixed-point underflow or overflow (result is too small or too large)" if k==8 then call sy "illegal filemode" @ a3 @ g4 if k==9 then call sy "a terminal screen (CRT) is required with the" @ a3 @ 'feature' if k==10 then if a3== then call sy "missing fileid for" g4

                        else call sy "illegal fileid" @ space(a3 a4 a5) @ g6

if k==11 then call sy "comparand operand must be an = or \= when using *xxx* type comparisons" if k==12 then call sy "not enough" choose('virtual storage',g4)", at least" a3 'are needed' if k==13 then do

             call sy "REXX syntax error"
             if isInt(a.6)  then call sy errortext(a.6)
             call syline
             end

if k==14 then call sy 'the' a5 "argument" a3 "can't be" choose('greater',a.7) "than" a6 a4 if k==15 then do

             if a3==  then call sy "division by zero"
                        else do
                             call sy 'raising a negative number' @ a3 @
                             call sy "to a negative or an odd fractional power" @ a4 @
                             call fto g5
                             end
             end

if k==16 then do

             call sy "illegal MDISK" g4 'address:' a3","
             call sy 'it must be exactly three hexadecimal characters  (but not 000),  or it may be'
             call sy "preceeded by an asterisk (*)  followed by three decimal characters"
             end

if k==17 then do

             call sy "undefined REXX variable referenced" a.6
             call syline
             end

if k==18 then do

             call sy "illegal MDISK address or filemode,"
             call sy "the 191 A MDISK address is reserved for the CMS user's private MDISK"
             end

if k==19 then call sy 'numeric digits ('comma(a6)") isn't sufficient to" a4 a5 'to' a3 if k==20 then call sy "the" a3 @ a4 'and' g5 @ "aren't alike" if k==21 then call sy choose("increment",a3) 'must be preceeded by a plus (+) or a minus (-)' if k==22 then do

             _='combination of characters:'
             if L.4==1  then _="character:"
             call sy a3 'contains an invalid' _ g4
             end

if k==23 then call sy "the" a3 choose("option",a5) "requires the" a4 choose('option or feature',g6) if k==24 then call sy "illegal" choose('volume',a4) "serial:" a3 ' (it must be six or less characters)' if k==25 then do

             call sy "you must be in the" a3 'mode/program to use the'
             call sy "specified command (or it's" g4 "option)"
             end

if k==26 then do

             call sy "illegal MDISK" g4 'address:' a3","
             call sy 'it must be exactly three hexadecimal characters  (but not 000)'
             end

if k==27 then call sy choose('number',g4) "can't be negative or zero (must be positive):" a3 if k==28 then call sy "duplicate" a3 'defined or specified:' g4 if k==29 then call sy "illegal filemode:" a3', it must be one character' if k==30 then do

             call say30
             if a5==a6 | a6== | a6==","  then call sy "it must be" space(aa5 g8 _b)
                                           else do
                                                _to='to'
                                                if a6==aa5+1  then _to="or"
                                                call sy 'it must be from' aa5 _to a6 _b
                                                end
             end

if k==31 then call sy "no lines (or incorrect lines) were put in the program stack" g3 if k==32 then call sy 'the command' a3 "exited, but it isn't supposed to exit or stop" if k==33 then call sy 'the' a3 "MDISK isn't a CMS MDISK, it's in the wrong format" if k==34 then call sy @ a3 a4 @ "can't be executed from the" a5 'MDISK' if k==35 then do

             call sy "no" choose('argument',a4) 'was specified after or'
             call fto a3 g5
             end

if k==36 then call sy 'file' @ g3 @ "can't exist on the" a5 'MDISK' if k==37 then do

             y=a3
             _=pos(a3,"`{[(«')
             if _\==0  then y=translate(word('single_quote double_quote grave_accent left_brace left_bracket left_parenthesis left_double_carrot',_),,"_") a3
             call sy 'unmatched' y g4
             end

if k==38 then call sy 'file' @ space(a3 a4 a5) @ choose("can't be located or is empty",g6) if k==39 then call sy "the" a3 choose('argument',a8) 'must be' a4 a5 "the" a6 choose('argument',a7) if k==40 then do

             call sy 'argument' @ a3 @ "isn't a valid hexadecimal string/number"
             call sy "(it contains a character other than 0123456789ABCDEFabcdef or a blank)"
             call fto g4
             end

if k==41 then do

             call sy "VM userid" @ g3 @ "doesn't exist or"
             call sy 'is illegal  (it may have an illegal character in it)'
             end

if k==42 then call sy "the MDISK" a4 'for the user' a3 "doesn't exist" if k==43 then call sy "illegal password for the" a3 a5 'MDISK was specified' if k==44 then do

             call sy "a CMS command is being used out of context,  or"
             call sy 'a command was renamed,  or the FSTs have been altered'
             _='DOS'
             if !cms  then _="CMS";call sy '(you may have to IPL' _")"
             end

if k==45 then call sy 'VM userid' @ g3 @ "isn't logged on" if k==46 then call sy "the file's" @ g4 "LRECL can't exceed" a3 if k==47 then call sy a3 @ a4 @ "not found" g5 if k==48 then do

             _=
             L=1
             if L.4==1 | right(aU.4,1)=='X'  then _=" an"
             if _==  then L=0
             call sy @ a3 g5 @ 'contains'_ "invalid character"s(L)':' a4
             end

if k==49 then call sy "CP LINK error for MDISK" a4 'userid' a3 if k==50 then do

             call sy 'illegal/invalid' a3 "specified" @ a4 @
             call fto g5
             end

if k==51 then call sy choose("documentation",a5) 'for' a3 a4 "couldn't be located" if k==52 then do

             call sy "arguments aren't permitted"
             call fto a4
             end

if k==53 then do

             call sy 'argument' @ a3 @ "isn't numeric" g5
             call fto a4
             end

if k==54 then do

             call sy "not enough" choose('arguments',a3) "were specified" g5
             call fto a4
             end

if k==55 then do

             call sy "illegal argument" @ a3 @ g5
             call fto a4
             end

if k==56 then call sy "illegal number of" choose('arguments',a4) "were specified" g5 a3 if k==57 then do

             y=choose("arguments",a3)
             z='was'
             if translate(right(y,1))=="S"  then z='were'
             call sy "no" y z "specified"
             end

if k==58 then call sy "only" g3 'argument's(a3) 'are accepted' if k==59 then do

             call sy "too many" choose('arguments',a3) "were specified" g5
             call fto a4
             end

if k==60 then call sy "argument#" a4 @ a3 @ 'must be an * or numeric' if k==61 then call sy "conflicting arguments:" g3 if k==62 then call sy choose('fileid1',a3) "and" choose('fileid2',a4) "can't be identical" g5 if k==63 then do

             call sy "no" 'argument was specified after or'
             call fto g3
             end

if k==64 then call sy "up to" g3 'argument's(a3) 'are accepted' if k==65 then call sy "bad argument" @ a3 @ "illegal use of" g4 if k==66 then call sy "only" a3 'to' a4 "arguments are accepted" if k==67 then call sy "unable to parse" a3 'from the results of:' g4 if k==68 then do

             call sy "return code" a3 'doing:'
             call sy g4
             i=a3
             end

if k==69 then call sy 'user' @ a3 @ "can't be logged on while the command" @ a2 @ 'is running' if k==70 then do

             if a3==2  then call sy "the" @ a2 @ 'command must be executed under the' a4 "userid"
             if a3==1  then call sy "the" @ a2 @ "command must be executed from the A MDISK"
             call sy "illegal use of the" @ a2 @ "command, subrc="a3
             end

if k==71 then call sy "can't attach a" g3 if k==72 then do

             call sy 'argument' @ a3 @ "isn't alphabetic" g5
             call fto a4
             end

if k==73 then do

             call sy "an attempt was made to execute an unauthorized or restricted command"
             if g3\==  then call sy g3
             end

if k==74 then call sy "the user" @ a3 @ 'must be in' a4 "mode" if k==75 then call sy "no" choose('write',a4) "access to the" @ choose('A',space(left(a3),1)) @ "MDISK" if k==76 then call sy a3 g5 "isn't known or supported:" a4 if k==77 then call sy space('error' a3 "in writing to disk file" @ g4 @) if k==78 then call sy choose("file",g6) @ a3 a4 a5 @ 'not found' if k==79 then call sy "the time window for execution is" a3 'through' a4 if k==80 then call sy @ a3 @ "isn't a known userid" if k==81 then do

             call sy 'argument' @ a5 space(@ g7) "is out of range"
             _=max(w.3,w.4)
             if L.3\==0  then call sy 'the lower limit is:' right(c.3,_)
             if L.4\==0  then call sy 'the upper limit is:' right(c.4,_)
             call fto a6
             end

if k==82 then call sy g4 @ a3 @ "can't be located" if k==83 then call sy "the" @ g3 @ 'option is required' if k==84 then call sy "file" @ g4 @ 'had a syntax error for' a3 if k==85 then call sy "illegal combination of arguments:" g4 if k==86 then do

             call sy "the" choose(a3,a2) 'command is being invoked out of context'
             if g4\==  then call sy g4
             end

if k==87 then do

             call sy 'argument' @ a3 @ "isn't a valid" choose('bit digit',a4)
             call sy '(it contains more than one binary digit)'
             call fto g5
             end

if k==88 then call sy g4 @ a3 @ "doesn't exist" if k==89 then call sy 'the' a3 "command can't be found" if k==90 then do

             call sy 'evaluation of' a3 "contains a zero divisor and"
             call sy 'the result is infinite' g4
             end

if k==91 then do

             call sy 'argument' @ a3 @ "isn't a valid" choose('bit string',a4)
             call sy '(it contains a non-binary character other than 0 or 1)'
             call fto g5
             end

if k==92 then do

             call sy choose('argument',a4) @ a3 @ "isn't a whole number (integer)" g7
             call fto a5
             end

if k==93 then call sy "file" @ g3 @ 'already exists' if k==94 then call sy "the T-DISK requested can't be obtained" if k==95 then call sy "not enough free storage can be obtained" if k==96 then call sy "illegal file" @ g3 @ 'or it was incorrectly modified' if k==97 then do

             call sy "a command failed,"
             if a3\==  then call sy "sub-command" @ g3 @','
             call sy "it's all or partially restricted to authorized users"
             end

if k==98 then do

             call sy "an attempt was made to execute the" @ a2 @ 'command while'
             call sy "the user" @ userid() @ "was in disconnected mode"
             end

if k==99 then call sy "illegal error number for the" !fn 'REXX EXEC' ":" g3 if a2\== then call sy "for the" @ a2 @ 'command or function.' call sy if errmsgnt\== & errmsgto\== then call sy "A notification (via $M) of this error has been sent to" errmsgto if !cms then @globalv 'SELECT' !fn "PURGE" if \isInt(i) then call er 53,i exit sign(oi)*i


/*═════════════════════════════general 1-line subs════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════*/ !all:  !!=!;!=space(!);upper !;call !fid;!nt=right(!var('OS'),2)=='NT';!cls=word('CLS VMFCLEAR CLRSCREEN',1+!cms+!tso*2);if arg(1)\==1 then return 0;if wordpos(!,'? ?SAMPLES ?AUTHOR ?FLOW')==0 then return 0;!call=']$H';call '$H' !fn !;!call=;return 1 !cal: if symbol('!CALL')\=="VAR" then !call=; return !call !env: !env='ENVIRONMENT'; if !sys=='MSDOS' | !brexx | !r4 | !roo then !env='SYSTEM'; if !os2 then !env='OS2'!env; !ebcdic=1=='f0'x; if !crx then !env='DOS'; return !fid: parse upper source !sys !fun !fid . 1 . . !fn !ft !fm .; call !sys; if !dos then do; _=lastpos('\',!fn); !fm=left(!fn,_); !fn=substr(!fn,_+1); parse var !fn !fn '.' !ft; end; return word(0 !fn !ft !fm,1+('0'arg(1))) !rex: parse upper version !ver !vernum !verdate .; !brexx='BY'==!vernum; !kexx='KEXX'==!ver; !pcrexx='REXX/PERSONAL'==!ver|'REXX/PC'==!ver; !r4='REXX-R4'==!ver; !regina='REXX-REGINA'==left(!ver,11); !roo='REXX-ROO'==!ver; call !env; return !sys: !cms=!sys=='CMS'; !os2=!sys=='OS2'; !tso=!sys=='TSO' | !sys=='MVS'; !vse=!sys=='VSE'; !dos=pos('DOS',!sys)\==0 | pos('WIN',!sys)\==0 | !sys=='CMD'; !crx=left(!sys,6)=='DOSCRX'; call !rex; return !var: call !fid; if !kexx then return space(dosenv(arg(1))); return space(value(arg(1),,!env)) $t: !call=']$T'; call "$T" arg(1); call=; return choose: parse arg c1,c2; if c2== | c2=="," then return c1; return c2 comma: procedure; parse arg _,c,p,t; c=pickBlank(c,","); o=p(p 3); p=abs(o); t=p(t 999999999); if \isInt(p) | \isInt(t) | p==0 | arg()>4 then return _; n=_'.9'; #=123456789; k=0; return comma_() comma_: if o<0 then do; b=verify(_,' '); if b==0 then return _; e=length(_)-verify(reverse(_),' ')+1; end; else do; b=verify(n,#,"M"); e=verify(n,#'0',,verify(n,#"0.",'M'))-p-1; end; do j=e to b by -p while k<t; _=insert(c,_,j); k=k+1;end;return _ er: parse arg _1,_2; call '$ERR' "14"p(_1) p(word(_1,2) !fid(1)) _2; if _1<0 then return _1; exit result erb: call sy; if a2\=="" then call sy '('!fn "was invoked by the" @ a2 @ 'EXEC)'; call er arg(1),arg(2) fto: parse arg fto ftox; ftoo='option'; if right(fto,2)=='()' then ftoo='function'; if fto\== then call sy "for the" ftoo @ space(fto ftox) @; return halt: call er .1 isInt: return datatype(arg(1),'W') isNum: return datatype(arg(1),'N') noValue: !sigl=sigl; call er 17,!fid(2) !fid(3) !sigl condition('D') sourceline(!sigl) opf: if right(arg(1),2)=='()' then return "function"; return 'option' p: return word(arg(1),1) pickBlank: procedure; parse arg x,y; arg xu; if xu=='BLANK' then return ' '; return p(x y) s: if arg(1)==1 then return arg(3); return p(arg(2) 's') say30: if a5==-1 then call sy 'illegal' a4":" a3; else call sy "illegal length of" a4":" a3; _t=p(a7 'character'); _b=_t || s(p(a6 aa5))" in length"; return sy: sy=arg(1); if length(sy)<81 then do; call syit sy; return; end; sysy=; do forever while sy\==; parse var sy _t sy; if length(sysy _t)<80 then do;sysy=sysy _t;iterate;end; call syitb;sysy=_t;end; if strip(sysy)\== then call syitb;return syfunc: if left(a6,1)==']' then do; _sl=g8; call sy "invocation of an undefined REXX function/subroutine" substr(a6,2); end; return syit: syit=arg(1); if xedit then address 'XEDIT' "EMSG" syit; else if a2=='$T' then say syit; else call $t etops syit; if errmsgto\== & syit\== then call '$M' errmsgto syit; return syitb: if left(sysy,1)==' ' then sysy=substr(sysy,2); call syit sysy; return syline: if a5\==0 then call sy 'on line' a5 "of" ufid; _sl=g7; call syfunc; if _sl\== then do; call sy; call sy "REXX sourceline is:"; call sy; call sy _sl; call sy; end; if !cms then do;'EXECSTAT' a2 a3;if rc==0 then "EXECDROP" a2 a3;end;return syntax: !sigl=sigl; call er 13,!fid(2) !fid(3) !sigl !cal() condition('D') sourceline(!sigl)</lang>

REXX Version 1 Messages

This is the   $SUDOKU.REX   (REXX) program and is used to solve the Rosetta Code task of "sudoku".

This REXX program was originally written to assist in sudoku puzzle solving (by giving strong hints), and not to solve the puzzle outright.
The REXX program was written to give increasing better hints and also show the possibilities (of what is possible solution for any cell),
and to partially solve the puzzle using distinct strategies (separately or in combination).   One option is to solve the puzzle.

The help for the   $SUDOKU   REXX program is included here ──► $SUDOKU.HEL.
The   $SUDOKU.REX   REXX program makes use of   $ERR.REX   REXX program which is used to display error messages (via   $T.REX).
The   $ERR.REX   REXX program is included here ──► $ERR.REX.
The   $SUDOKU.REX   REXX program makes use of   $T.REX   REXX program which is used to display text messages.
The   $T.REX   REXX program is included here ──► $T.REX.
Some older REXXes don't have a   changestr   BIF, so one is included here ──► CHANGESTR.REX.
REXX programs not included are   $H   which shows help and other documentation. <lang rexx>/*REXX program displays, can give hints, and/or solve a sudoku puzzle. */ trace off parse arg ! if !all(arg()) then exit if !cms then address signal on halt signal on noValue signal on syntax

ops=! /*remove extraneous blanks.*/ numeric digits 20 combos=1 @.=' ' /*initialize grid to blanks*/ !.= /*nullify valid empty# list*/ @abc='abcdefghijklmnopqrstuvwxyz' @abcU=@abc upper @abcU colors=!cms | !pcrexx | !r4 | !roo /*Are colors supported ? */ clear=1 /*option: clear the screen.*/ highLight=0 /*option: highlight singles*/ pruneall=0 /*option: prune all. */ prunemats=0 /*option: prune matches. */ prunesing=0 /*option: prune singles. */ pruneexcl=0 /*option: prune exclusives.*/ pruneline=0 /*option: prune lines. */ pruneonly=0 /*option: prune onlys. */ simple=0 /*option: show simple boxes*/ showoneline=0 /*option: show grid as1line*/ showgrid=1 /*option: show the grid. */ showinfo=1 /*option: show informatiion*/ showposs=0 /*option: show possible val*/ showcomb=0 /*option: show combinations*/ showrow= /*option: SHOWPOSS for rowN*/ showcol= /*option: SHOWPOSS for colN*/ showbox= /*option: SHOWPOSS for boxN*/ showcell= /*option: SHOWPOSS cellRC */ short=0 solve=0 /*option: solve the puzzle.*/ sod=lower(translate(!fn,,'$')) /*name of the puzzle. */ tellinvalid=1 /*tell err msg if invalid X*/ tops= /*option: used for $T opts.*/

gridindents=3 /*# spaces grid is indented*/ gridindent=left(,gridindents) /*spaces indented for grid.*/ gridwidth=7 /*grid cell interior width.*/ gridbar='b3'x /*bar for the grid (cells).*/ gridlt='da'x /*grid cell left top. */ gridrt='bf'x /*grid cell right top. */ gridlb='c0'x /*grid cell left bottom. */ gridrb='d9'x /*grid cell right bottom. */ gridline='c4'x /*grid cell line (hyphen). */ gridlin=copies(gridline,gridwidth) /*grid cell total line. */ gridemp=left(,gridwidth) /*grid cell empty (spaces).*/ griddj='c2'x /*grid cell down junction.*/ griduj='c1'x /*grid cell up junction.*/ gridlj='c3'x /*grid cell left junction.*/ gridrj='b4'x /*grid cell right junction.*/ gridcross='c5'x /*grid cell cross junction.*/

 do  while ops\==                         /*parse any and all options*/
 parse var ops _1 2 1 _ . 1 _o ops
 upper _
   select
   when _==','                    then nop
   when _1=='.' & pos("=",_)\==0  then tops=tops _o
   when  abb('PUZzle')            then      /*do PUZZ (whole) placement*/
        do
        puzz=na()
        if length(puzz)>81  then call er 30,puzz 'PUZZLE 1───►81'
                        do j=1  for length(puzz)
                        q=substr(puzz,j,1)
                        if q=='.'  then iterate
                        call vern q,'PUZZLE_digit'
                        c=j//9
                        if c==0  then c=9
                        r=(j-1)%9 + 1
                        @.r.c=q
                        end   /*j*/
        end
   when _=='CELL' then                      /*do CELL (grid) placement.*/
        do
        rc=nai()
        if length(rc)\==2                   then call er 30,y 'CELL'rc 2
        y=na()
        if length(y)>1                      then call er 30,y 'CELL'rc 1
        r=left(rc,1)
        c=right(rc,1)
        call vern r,'CELLrow'
        call vern c,'CELLcolumn'
        call vern y,'CELLdigit'
        @.r.c=y
        end
   when  abb('COLumn')  then                /*do ROW (grid) placement. */
        do
        n=nai()
        y=na()
        call vern n,'column'
        ly=length(y)
        if ly>9  then call er 30,y 'column'n '1───>9'
                        do j=1  for ly
                        x=substr(y,j,1)
                        if x== | x=="_" | x=='*' | x=="."  then iterate
                        if \isInt(x)  then call er 92,x 'cell_for_column'n
                        @.j.n=x
                        end   /*j*/
        end
   when  abb('ROW')  then                   /*do ROW (grid) placement. */
        do
        n=nai()
        y=na()
        call vern n,'row'
        ly=length(y)
        if ly>9  then call er 30,y 'row'n '1───>9'
                        do j=1  for ly
                        x=substr(y,j,1)
                        if x== | x=="_" | x=='*' | x=="."  then iterate
                        if \isInt(x)  then call er 92,x 'cell_for_row_'n
                        @.n.j=x
                        end   /*j*/
        end
   when abbn('CLearscreen')        then clear=no()
   when abbn('HIGHLightsingles')   then highLight=no()
   when abbn('PRUNEALL')           then pruneall=no()
   when abbn('PRUNEONLYs')         then pruneonly=no()
   when abbn('PRUNEEXclusives')    then pruneexcl=no()
   when abbn('PRUNELINEs')         then pruneline=no()
   when abbn('PRUNEMATches')       then prunemats=no()
   when abbn('PRUNESINGles')       then prunesing=no()
   when abbn('SIMPle')             then simple=no()
   when  abb('SHOWBOXes')|,
         abb('SHOWBOXs')           then showbox=nai()
   when  abb('SHOWCELLs')          then showcell=translate(na(),,',')
   when  abb('SHOWCOLs')           then showcol=nai()
   when abbn('SHOWCOMBinations')   then showcomb=no()
   when abbn('SHOWGrid')           then showgrid=no()
   when abbn('SHOWINFOrmation')    then showinfo=no()
   when abbn('SHOWONELINE')        then showoneline=no()
   when abbn('SHOWPOSSibles') then showposs=no()
   when  abb('SHOWROWs')           then showrow=nai()
   when abbn('SHortgrid')          then short=no()
   when abbn('SOLvepuzzle')        then solve=no()
   otherwise                       call er 55,_o
   end   /*select*/
 end     /*while ops¬==*/

if solve then pruneall=1 /*if solving, use PRUNEALL.*/

if pruneall then do /*if pruneAll, set ON other*/

                 pruneexcl=1
                 pruneonly=1
                 pruneline=1
                 prunemats=1
                 prunesing=1
                 end

aprune = , /*is there a PRUNExxx on ? */

                 pruneexcl |,
                 pruneonly |,
                 pruneline |,
                 prunemats |,
                 prunesing

if highLight then do /*HIGHLIGHTSINGLES opt on? */

                  hLl='-'
                  hLr='-'
                  if colors  then do
                                  hLl='('
                                  hLr=')'
                                  tops='.H=yell' tops
                                  end
                  end

tops=space(tops) box.=

 do j=1  for 9                              /*build the box bounds.    */
 rr=(((j*3)%10)+1)*3-2                      /*compute row lower bound. */
 cc=(((j-1)//3)+1)*3-2                      /*compute col lower bound. */
 boxr.j=rr
 boxc.j=cc
                       do   r=rr  to rr+2   /*build boxes with cell #s.*/
                         do c=cc  to cc+2
                         rc=r || c
                         box.j=box.j rc
                         box.rc=j
                         end   /*c*/
                       end     /*r*/
 box.j=strip(box.j)
 end   /*j*/

rowlb.=10 /*row R, low box number=b.*/ collb.=10 /*col R, low box number=b.*/ boxlr.=10 /*box B, low row number=r.*/ boxlc.=10 /*box B, low col number=c.*/

 do   r=1  for 9
   do c=1  for 9
   rc=r || c
   b=box.rc                                 /*what box is this R,C in ?*/
   rowlb.r=min(rowlb.r,b)                   /*find min box # for row R.*/
   collb.c=min(collb.c,b)                   /*find min box # for col C.*/
   boxlr.b=min(boxlr.b,r)                   /*find min row # for box B.*/
   boxlc.b=min(boxlc.b,c)                   /*find min col # for box B.*/
   end   /*c*/
 end     /*r*/
do j=1  to 9                                /*for each box, row, col...*/
rowhb.j=rowlb.j+2                           /*compute row's high box #.*/
colhb.j=collb.j+6                           /*compute col's high box #.*/
boxhr.j=boxlr.j+2                           /*compute box's high row #.*/
boxhc.j=boxlc.j+6                           /*compute box's high col #.*/
end   /*j*/

if showgrid then call showgrid 'the puzzle' /*show the grid to screen ?*/ if \validall() then exit /*validate specified digits*/ tellinvalid=0 /*don't tell err messages. */ !.= /*nullify valid empty# list*/ call buildposs /*build possible values. */ if showposs then call showgrid 'puzzle possibles' /*show 1st possibles?*/ if \validate(1) then exit /*validate the puzzle. */

if showoneline then do /*show grid as line line ? */

                    _=                      /*start with a clean slate.*/
                          do   r=1  for 9
                            do c=1  for 9
                            _=_ || @.r.c    /*build the string ...     */
                            end   /*c*/
                          end     /*r*/
                    _=translate(strip(_,'T'),".",' ')
                    if showinfo  then call $T 'one-line grid:'
                    call $T _
                    end

if aprune |,

  showposs then do
                call pruneposs              /*go build poss, then prune*/
                if showposs then call showgrid 'possibles' /*show grid.*/
                if \validate(1) then exit   /*validate the puzzle.     */
                end

if combos==1 then call $t sod 'puzzle solved.'

             else  if showcomb  then call $t 'combinations='comma(combos)

exit /*stick a fork in it, we're done.*/

/*─────────────────────────────vern subroutine──────────────────────────*/ vern: parse arg v,w /*verify a digit for an opt*/ if v== then call er 35,v w if \isInt(v) then call er 92,v w if v<1 | v>9 then call er 81,1 9 v w return

/*─────────────────────────────buildposs subroutine─────────────────────*/ buildposs: !.= /*nullify possibilities. */ combos=1

 do   rp=1  for 9                           /*build table of valid #s. */
   do cp=1  for 9                           /*step through each column.*/
   if @.rp.cp\==' '  then iterate           /*not blank?  Keep looking.*/
                         do jd=1  for 9     /*try each digit.          */
                         @.rp.cp=jd
                         if validx(rp,cp) then !.rp.cp=!.rp.cp || jd
                         end   /*jd*/
   combos=combos*length(!.rp.cp)            /*calculate # combinations.*/
   @.rp.cp=' '                              /*restore the point (blank)*/
   end      /*cp*/
 end        /*rp*/

return

/*─────────────────────────────showgrid subroutine──────────────────────*/ showgrid: parse arg title if clear then !cls /*clear the screen ? */ if title\== & showinfo then call $t !fn 'is showing' title gtail=copies3(gridlb || gridlin || copies2(griduj || gridlin) || gridrb) ghead=copies3(gridlt || gridlin || copies2(griddj || gridlin) || gridrt) call tg ghead gemp=copies3(copies3(gridbar || gridemp)gridbar) grid=copies3(gridlj || gridlin || copies2(gridcross || gridlin)gridrj) anyshow= \ ((showcell || showcol || showrow || showbox)\==)

 do jr=1  for 9
 if \short  then call tg gemp
 gnum=
   do jc=1  for 9
   _=@.jr.jc
   if _\==' ' & highLight  then _=hLl || _ || hLr
   if _==' ' & ,
      showposs  then do
                     jrjc=jr || jc
                     showit=anyshow
                     if showcell\== then if wordpos(jrjc,showcell)\==0 then showit=1
                     if showcol\==  then if pos(jc,showcol)\==0  then showit=1
                     if showrow\==  then if pos(jr,showrow)\==0  then showit=1
                            do jb=1  while  showbox\==
                            b=substr(showbox,jb,1)
                            if b==' '                   then leave
                            if wordpos(jrjc,box.b)\==0  then showit=1
                            end   /*jb*/
                     if showit  then _=strip(left(!.jr.jc,gridwidth),'T')
                     end
   gnum=gnum || gridbar || centre(_,gridwidth)
   if jc//3==0  then gnum=gnum || gridbar
   end   /*jc*/
 call tg gnum
 if \short  then call tg gemp
 if jr//3==0 then do
                  call tg gtail
                  if jr\==9  then call tg ghead
                  end
             else call tg grid
 end   /*jr*/

call $t return

/*─────────────────────────────validate subroutine──────────────────────*/ validate: /*are all empties possible?*/

 do   r=1  for 9                            /*step through each row.   */
   do c=1  for 9                            /*step through each column.*/
   if @.r.c==' ' & ,
      !.r.c==  then do                     /*no legal digit here.     */
                      if arg(1)==1  then call $t sod "puzzle isn't valid !"
                      return 0
                      end
   end   /*c*/
 end     /*r*/                              /*sub requires possibles.  */

return 1 /*indicate puzzle is valid.*/

/*─────────────────────────────validall subroutine──────────────────────*/ validall: /*validate all Q specified.*/

 do   r=1  for 9                            /*step through each row.   */
   do c=1  for 9                            /*step through each column.*/
   if @.r.c==' '  then iterate              /*if blank, then it's ok.  */
   y=                                       /*the rest of the row.     */
   rc=r||c
               do kc=1  for 9               /*compare to #s in column. */
               if kc\==c  then y=y|| @.r.kc /*build the rest of the row*/
               end   /*kc*/
   q=@.r.c
   if pos(q,y)\==0  then return tem(r,c,'row')    /*same # in same row?*/
   y=                                       /*the rest of the column.  */
               do kr=1  for 9               /*compare to #s in column. */
               if kr\==r then y=y || @.kr.c /*build the rest of the col*/
               end      /*kr*/
   if pos(q,y)\==0  then return tem(r,c,'col')    /*same # in same col?*/
   y=                                       /*the rest of the box.     */
   b=box.rc
     do   br=boxr.b  to boxr.b+2            /*compare to #s of the box.*/
       do bc=boxc.b  to boxc.b+2            /*build the rest of the box*/
       if br\==r & bc\==c  then y=y || @.br.bc
       end  /*bc*/
     end    /*br*/
   if pos(q,y)\==0  then return tem(r,c,'box')    /*same # in same box?*/
   end   /*c*/
 end     /*r*/

return 1 /*indicate all are valid.*/

/*─────────────────────────────validx subroutine────────────────────────*/ validx: arg r,c rc=r || c y= /*the rest of the row. */

          do kc=1  for 9                    /*compare to #s in column. */
          if kc\==c  then y=y || @.r.kc     /*build the rest of the row*/
          end   /*kc*/

q=@.r.c /*get the digit at r,c */ if pos(q,y)\==0 then return tem(r,c,'row') /*same number in same row ?*/ y= /*the rest of the column. */

     do kr=1  for 9                         /*compare to #s in column. */
     if kr\==r  then y=y || @.kr.c          /*build the rest of the col*/
     end   /*kr*/

if pos(q,y)\==0 then return tem(r,c,'col') /*same # in same column ?*/ y= /*the rest of the box. */ b=box.rc

          do   br=boxr.b  to boxr.b+2       /*compare to #s of the box.*/
            do bc=boxc.b  to boxc.b+2       /*build the rest of the box*/
            if br==r & bc==c  then iterate
            y=y || @.br.bc
            end   /*br*/
          end     /*bc*/

if pos(q,y)\==0 then return tem(r,c,'box') /*same # in same box ? */ return 1 /*indicate X (r,c) is valid*/

/*─────────────────────────────pruneposs subroutine─────────────────────*/ pruneposs: if \(prunesing | pruneexcl | prunemats | pruneline) then return call buildposs

 do prunes=1
 call $t !fn 'is starting prune pass #' prunes
 found=0                                    /*indicate no prunes so far*/
 if prunesing then do                       /*prune puzzle for singles.*/
                   _=prunesing()            /*find any singles ?       */
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if pruneexcl then do                       /*prune puzzle for singles.*/
                   _=pruneexcl()            /*find any excluives ?     */
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if pruneonly then do                       /*prune puzzle for onlys.  */
                   _=pruneonly()            /*find any onlys ?         */
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if prunemats then do jpm=2 to 8            /*prune puzzle for matches.*/
                   _=prunemats(jpm)         /*find any matches (len=j)?*/
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if pruneline then do                       /*prune puzzle for lines.  */
                   _=pruneline()            /*find 2 or more on a line?*/
                   found=found | _          /*track if anything found. */
                   if _ then if showgrid then call showgrid /*show grid*/
                   end
 if \found then leave                       /*nothing found this time ?*/
 end    /*prunes*/

return

/*─────────────────────────────prunesing subroutine─────────────────────*/ prunesing: foundsing=0

   do   r=1  for 9
     do c=1  for 9
     _=length(!.r.c)                        /*get length of possible.  */
     if _==0   then iterate                 /*if null, then ignore it. */
     if _\==1  then iterate                 /*if not one digit, ignore.*/
     @.r.c=!.r.c                            /*it's 1 digit, a solution.*/
     !.r.c=                                 /*erase the old possible.  */
     foundsing=1
     call $t !fn 'found a single digit at cell' drc(r,c,@.r.c)
     end   /*c*/
   end     /*r*/

if foundsing then call buildposs /*re-build the possibles. */ return foundsing

/*─────────────────────────────pruneexcl subroutine─────────────────────*/ pruneexcl: foundexcl=0

 do exclusives=1                            /*keep building possibles. */
   do   r=1  for 9
     do c=1  for 9
     z=!.r.c
     lz=length(z)                           /*get length of possible.  */
     if lz==0  then iterate                 /*if null, then ignore it. */
     y=
     rc=r || c
     b=box.rc
               do   br=boxr.b  to boxr.b+2  /*compare to #s of the box.*/
                 do bc=boxc.b  to boxc.b+2  /*build the rest of the box*/
                 if br==r & bc==c  then iterate
                 y=y || @.br.bc || !.br.bc
                 end   /*bc*/
               end     /*br*/
                                            /*test for reduction.      */
      do t=1  for lz
      q=substr(z,t,1)
      if pos(q,y)==0 then do
                          foundexcl=1
                          @.r.c=q           /*it's a singularity, a sol*/
                          !.r.c=            /*erase old possibleity.   */
                          call $t !fn 'found the digit' q,
                                 "by exclusiveness at cell" drc(r,c,z)
                          call buildposs    /*re-build the possibles.  */
                          iterate exclusives
                          end
      end  /*t*/
     end   /*c*/
   end     /*r*/
 leave
 end       /*exclusives*/

return foundexcl

/*─────────────────────────────prunemats subroutine─────────────────────*/ prunemats: foundmatch=0 /*no matches found so far. */ parse arg L /*length of match, L=2,pair*/

 do matches=1
   do   r=1  for 9
     do c=1  for 9
     _=length(!.r.c)                        /*get length of possible.  */
     if _==0   then iterate                 /*if null, then ignore it. */
     if _\==L  then iterate                 /*not right length, ignore.*/
     qq=!.r.c
     m=0                                    /*count of matches so far. */
            do _c=1  for 9                  /*nother match in same row?*/
            if qq==!.r._c  then m=m+1       /*up count if it's a match.*/
            end  /*_c*/
     if m>=L then do pc=1  for 9            /*squish other possibles.  */
                  old=!.r.pc                /*save the "old" value.    */
                  if old==qq   then iterate /*if match, then ignore it.*/
                  if old==   then iterate /*if null poss, then ignore*/
                  new=squish(old,qq)        /*remove mat's digs from X.*/
                  if new==old  then iterate /*if no change,keep looking*/
                  !.r.pc=new                /*store new value into old.*/
                  foundmatch=1              /*indicate match was found.*/
                  call $t !fn 'is removing a'  old "from"  drc(r,pc,old),
                              'because of a match at'     drc(r,c,qq)
                  if length(new)==1 then do             /*reduce if L=1*/
                                         @.r.pc=new     /*store single.*/
                                         !.r.pc=        /*delete poss. */
                                         call buildposs /*re-build poss*/
                                         iterate matches  /*start over.*/
                                         end
                  end    /*pc*/
     m=0                                    /*count of matches so far. */
            do _r=1  for 9                  /*nother match in same col?*/
            if qq==!._r.c  then m=m+1       /*up count if it's a match.*/
            end   /*_r*/
     if m>=L then do pr=1  for 9            /*squish other possibles.  */
                  old=!.pr.c                /*save the "old" value.    */
                  if old==qq then iterate   /*if match, then ignore it.*/
                  if old== then iterate   /*if null poss, then ignore*/
                  new=squish(old,qq)        /*remove mat's digs from X.*/
                  if new==old then iterate  /*if no change,keep looking*/
                  !.pr.c=new                /*store new value into old.*/
                  foundmatch=1              /*indicate match was found.*/
                  call $t !fn 'is removing a'  old  "from" drc(pr,c,old),
                              'because of a match at' drc(r,c,qq)
                  if length(new)==1 then do             /*reduce if L=1*/
                                         @.pr.c=new     /*store single.*/
                                         !.pr.c=        /*delete poss. */
                                         call buildposs /*re-build poss*/
                                         iterate matches  /*start over.*/
                                         end
                  end   /*pr*/
     end                /*c*/
   end                  /*r*/
 leave
 end                    /*matches*/

return foundmatch

/*─────────────────────────────pruneonly subroutine─────────────────────*/ pruneonly: foundmatch=0 /*no matches found so far. */

 do findonlys=1                             /*keep searching ...       */
 _row.=                                     /*build str for each row . */
          do   r=1  for 9
            do c=1  for 9
            if !.r.c\==  then _row.r=_row.r !.r.c
            end   /*c*/
          end     /*r*/
 _col.=                                     /*build str for each boxcol*/
          do   c=1  for 9
            do r=1  for 9
            if !.r.c\==  then _col.c=_col.c !.r.c
            end   /*r*/
          end     /*c*/
   do   r=1  for 9
     do c=1  for 9
     q=!.r.c
     if q==  then iterate                 /*if empty, then ignore it.*/
       do j=1  to length(q)                 /*step through each digit. */
       k=substr(q,j,1)
       if kount1(k,_row.r) |,               /*is this the ONLY digit K?*/
          kount1(k,_col.c) then do i=1  to length(q)    /*prune others.*/
                                foundmatch=1
                                _=substr(q,i,1)
                                if _==k  then iterate   /*if=K, ignore.*/
                                o=squish(q,_)           /*remove others*/
                                !.r.c=o
                                call $t !fn  'removed part of an only',
                                             _   "from cell"   drc(r,c,q)
                                if length(o)==1  then   /*reduce if L=1*/
                                  do
                                  @.r.c=o               /*store single.*/
                                  !.r.c=                /*delete poss. */
                                  call buildposs        /*re-build poss*/
                                  iterate findonlys     /*start over.  */
                                  end
                                end   /*i*/
       end   /*j*/
     end     /*c*/
   end       /*r*/
 leave
 end     /*findonlys*/

return foundmatch

/*─────────────────────────────pruneline subroutine─────────────────────*/ pruneline: foundmatch=0 /*no matches found so far. */

do findlines=1                              /*keep searching ...       */
_boxr.=                                     /*build str for each boxrow*/
          do   r=1  for 9
            do c=1  for 9
            rc=r || c
            b=box.rc
            if !.r.c\==  then _boxr.r.b=strip(_boxr.r.b !.r.c)
            end   /*c*/
          end     /*r*/
 _boxc.=                                    /*build str for each boxcol*/
          do   c=1  for 9
            do r=1  for 9
            rc=r || c
            b=box.rc
            if !.r.c\==  then _boxc.c.b=strip(_boxc.c.b !.r.c)
            end   /*r*/
          end     /*c*/
 do r=1  for 9                              /*search all rows for twins*/
   do b=rowlb.r  to rowhb.r                 /*for each row, search box.*/
   aline=_boxr.r.b                          /*get a  row  in the box.  */
   if aline==  then iterate               /*if empty, ignore the line*/
   w=words(aline)                           /*W  is # of words in aline*/
   if w<2        then iterate               /*if < 2 words, ignore line*/
     do k=1  for 9                          /*search for each digit.   */
     f=pos(k,aline)                         /*pos of the 1st digit:  k */
     if f==0  then  iterate                 /*no dig k, so keep looking*/
     s=pos(k,aline,f+1)                     /*pos of the 2nd digit:  k */
     if s==0  then  iterate                 /*no 2nd k, so keep looking*/
       do jr=rowlb.r  to rowhb.r            /*look at the other 2 rows.*/
       if jr==r  then  iterate              /*if the same row, ignore. */
       if pos(k,_boxr.jr.b)\==0  then iterate k /*if no digit K, ignore*/
       end   /*jr*/
                                            /*found 2 Ks in row R box B*/
        do jb=rowlb.r  to rowhb.r           /*search boxes row R for K.*/
        if jb==b  then iterate              /*ignore if in the same box*/
        if pos(k,_boxr.r.jb)==0  then iterate
        foundmatch=1                        /*found a K in col C box JB*/
          do kc=1  for 9                    /*find which cell  K is in.*/
          rc=r || kc
          if box.rc==b        then iterate  /*ignore if in the same box*/
          _=!.r.kc
          if _==            then iterate  /*ignore if no possible.   */
          if pos(k,_)==0      then iterate  /*if no digit  K,  ignore. */
          call $t  !fn   'is row-line pruning digit' k,
                         'from cell'    drc(r,kc,!.r.kc)
          !.r.kc=squish(_,k)                /*remove mat's digs from X.*/
          if length(!.r.kc)==1  then do     /*pruned down to one digit?*/
                                     @.r.kc=!.r.kc  /*make a true digit*/
                                     !.r.kc=        /*erase possibility*/
                                     call buildposs /*rebuild possibles*/.
                                     iterate findlines
                                     end
          end   /*kc*/
        end     /*jb*/
     end        /*k*/
   end          /*b*/
 end            /*r*/
 do c=1  for 9                              /*search all cols for twins*/
   do b=collb.c  to colhb.c  by 3           /*for each col, search box.*/
   aline=_boxc.c.b                          /*get a  column in the box.*/
   if aline==  then iterate               /*if empty, ignore line*/
   w=words(aline)
   if w<2  then iterate                     /*if < 2 words, ignore line*/
     do k=1  for 9                          /*search for each digit.   */
     f=pos(k,aline)                         /*pos of the 1st digit:  k */
     if f==0  then iterate                  /*no dig k, so keep looking*/
     s=pos(k,aline,f+1)                     /*pos of the 2nd digit:  k */
     if s==0  then iterate                  /*no 2nd k, so keep looking*/
       do jc=boxlc.b  to boxhc.b            /*look at the other 2 cols.*/
       if jc==c  then iterate               /*if the same col, ignore. */
       if pos(k,_boxc.jc.b)\==0  then iterate k /*if no digit K, ignore*/
       end   /*jc*/
                                            /*found 2 Ks in col C box B*/
        do jb=collb.c  to colhb.c by 3      /*search boxes col C for K.*/
        if jb==b  then iterate              /*ignore if in the same box*/
        if pos(k,_boxc.c.jb)==0  then iterate
        foundmatch=1                        /*found a K in col C box JB*/
          do kr=1  for 9                    /*find which cell  K is in.*/
          rc=kr || c
          if box.rc==b       then iterate   /*ignore if in the same box*/
          _=!.kr.c
          if _==           then iterate   /*ignore if no possible.   */
          if pos(k,_)==0     then iterate   /*if no digit  K,  ignore. */
          call $t !fn  'is col-line pruning digit'  k,
                       'from cell'    drc(kr,c,!.kr.c)
          !.kr.c=squish(_,k)                /*remove mat's digs from X.*/
          if length(!.kr.c)==1  then do     /*pruned down to one digit?*/
                                     @.kr.c=!.kr.c  /*make a true digit*/
                                     !.kr.c=        /*erase possibility*/
                                     call buildposs /*rebuild possibles*/.
                                     iterate findlines
                                     end
          end   /*kr*/
        end     /*jb*/
     end        /*k*/
   end          /*b*/
 end            /*c*/
leave
end     /*findlines*/

return foundmatch

/*═════════════════════════════general 1-line subs════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════════*/ !all:!!=!;!=space(!);upper !;call !fid;!nt=right(!var('OS'),2)=='NT';!cls=word('CLS VMFCLEAR CLRSCREEN',1+!cms+!tso*2);if arg(1)\==1 then return 0;if wordpos(!,'? ?SAMPLES ?AUTHOR ?FLOW')==0 then return 0;!call=']$H';call '$H' !fn !;!call=;return 1 !cal: if symbol('!CALL')\=="VAR" then !call=; return !call !env: !env='ENVIRONMENT'; if !sys=='MSDOS' | !brexx | !r4 | !roo then !env='SYSTEM'; if !os2 then !env='OS2'!env; !ebcdic=1=='f0'x; if !crx then !env='DOS'; return !fid: parse upper source !sys !fun !fid . 1 . . !fn !ft !fm .; call !sys; if !dos then do; _=lastpos('\',!fn); !fm=left(!fn,_); !fn=substr(!fn,_+1); parse var !fn !fn '.' !ft; end; return word(0 !fn !ft !fm,1+('0'arg(1))) !rex: parse upper version !ver !vernum !verdate .; !brexx='BY'==!vernum; !kexx='KEXX'==!ver; !pcrexx='REXX/PERSONAL'==!ver | 'REXX/PC'==!ver; !r4='REXX-R4'==!ver; !regina='REXX-REGINA'==left(!ver,11); !roo='REXX-ROO'==!ver; call !env; return !sys: !cms=!sys=='CMS'; !os2=!sys=='OS2'; !tso=!sys=='TSO' | !sys=='MVS'; !vse=!sys=='VSE'; !dos=pos('DOS',!sys)\==0 | pos('WIN',!sys)\==0 | !sys=='CMD'; !crx=left(!sys,6)=='DOSCRX'; call !rex; return !var: call !fid; if !kexx then return space(dosenv(arg(1))); return space(value(arg(1),,!env)) $fact!: procedure; parse arg x _ .; l=length(x); n=l-length(strip(x,'T',"!")); if n<=-n | _\== | arg()\==1 then return x; z=left(x,l-n); if z<0 | \isInt(z) then return x; return $fact(z,n) $fact: procedure; parse arg x _ .; arg ,n ! .; n=p(n 1); if \isInt(n) then n=0; if x<-n | \isInt(x) | n<1 | _ || !\== | arg()>2 then return x || copies("!",max(1,n)); !=1; s=x//n; if s==0 then s=n; do j=s to x by n; !=!*j; end; return ! $sfxa: parse arg ,s,m; arg u,c; if pos(left(s,2),u)\==0 then do j=length(s) to compare(s,c)-1 by -1; if right(u,j)\==left(c,j) then iterate; _=left(u,length(u)-j); if isNum(_) then return m*_; leave; end; return arg(1) $sfxf: parse arg y; if right(y,1)=='!' then y=$fact!(y); if \isNum(y) then y=$sfxz(); if isNum(y) then return y; return $sfxm(y) $sfxm: parse arg z; arg w; b=1000; if right(w,1)=='I' then do; z=shorten(z); w=z; upper w; b=1024; end; p=pos(right(w,1),'KMGTPEZYXWVU'); if p==0 then return arg(1); n=shorten(z); r=num(n,f,1); if isNum(r) then return r*b**p; return arg(1) $sfxz: return $sfxa($sfxa($sfxa($sfxa($sfxa($sfxa(y,'PAIRs',2),'DOZens',12),'SCore',20),'GREATGRoss',1728),'GRoss',144),'GOOGOLs',1e100) $t: if tops== then say arg(1); else do; !call=']$T'; call "$T" tops arg(1); !call=; end; return ab: arg ab,abl; return abbrev(ab,_,abl) abb: arg abbu; parse arg abb; return abbrev(abbu,_,abbl(abb)) abbl: return verify(arg(1)'a',@abc,'M')-1 abbn: parse arg abbn; return abb(abbn) | abb('NO'abbn) abn: arg ab,abl; return abbrev(ab,_,abl) | abbrev('NO'ab,_,abl+2) comma: procedure; parse arg _,c,p,t; c=pickBlank(c,","); o=p(p 3); p=abs(o); t=p(t 999999999); if \isInt(p) | \isInt(t) | p==0 | arg()>4 then return _; n=_'.9'; #=123456789; k=0; return comma_() comma_: if o<0 then do; b=verify(_,' '); if b==0 then return _; e=length(_)-verify(reverse(_),' ')+1; end; else do; b=verify(n,#,"M"); e=verify(n,#'0',,verify(n,#"0.",'M'))-p-1; end; do j=e to b by -p while k<t; _=insert(c,_,j); k=k+1; end; return _ copies2: return copies(arg(1),2) copies3: return copies(arg(1),3) drc: procedure; parse arg r,c,p; _=r","c; if p\== then _=_ "("p')'; return _ er: parse arg _1,_2; call '$ERR' "14"p(_1) p(word(_1,2) !fid(1)) _2; if _1<0 then return _1; exit result err: call er '-'arg(1),arg(2); return erx: call er '-'arg(1),arg(2); exit halt: call er .1 int: int=num(arg(1),arg(2)); if \isInt(int) then call er 92,arg(1) arg(2); return int/1 isInt: return datatype(arg(1),'W') isNum: return datatype(arg(1),'N') kount1: parse arg qd,string; k1=pos(qd,string); if k1==0 then return 0; return pos(qd,string,k1+1)==0 lower: return translate(arg(1),@abc,translate(@abc)) na: if arg(1)\== then call er 01,arg(2); parse var ops na ops; if na== then call er 35,_o; return na nai: return int(na(),_o) nail: return squish(int(translate(na(),0,','),_o)) nan: return num(na(),_o) no: if arg(1)\== then call er 01,arg(2); return left(_,2)\=='NO' noValue:!sigl=sigl; call er 17,!fid(2) !fid(3) !sigl condition('D') sourceline(!sigl) num: procedure; parse arg x .,f,q; if x== then return x; if isNum(x) then return x/1; x=space(translate(x,,','),0); if \isNum(x) then x=$sfxf(x); if isNum(x) then return x/1; if q==1 then return x; if q== then call er 53,x f; call erx 53,x f p: return word(arg(1),1) pickBlank: procedure; parse arg x,y; arg xu; if xu=='BLANK' then return ' '; return p(x y) shorten:procedure; parse arg a,n; return left(a,max(0,length(a)-p(n 1))) simple: return translate(arg(1),'.||--%<>AV'copies('+',25),"·│║─═☼◄►↑↓┤┐└┴┬├┼┘┌╔╗╚╝╟╢╞╡╫╪╤╧╥╨╠╣") squish: return space(translate(arg(1),,word(arg(2) ',',1)),0) syntax: !sigl=sigl; call er 13,!fid(2) !fid(3) !sigl !cal() condition('D') sourceline(!sigl) tem: parse arg r,c,w; if tellinvalid then say '***error!*** row' r", col" c '('@.r.c") is a duplicate of another in the same" w'.'; return 0 tg: arg tg; if simple then tg=simple(tg); call $t gridindent || tg; return</lang>

REXX CHANGESTR function

This version of the   changestr   BIF has more functionality than the standard BIF.

<lang rexx>/*REXX program emulates the CHANGESTR built-in function for older REXXes*/ /*──── This version has more functionality: limit the number of changes.*/ /*──── start of change occurrence#.*/ /*──── start of change position. */

/*╔══════════════════════════ CHANGESTR function ══════════════════════╗ ╔═╩════════════════════════════════════════════════════════════════════╩═╗ ║ The CHANGESTR function is used to replace some or all occurrences of an║ ║ (old) string in a haystack with a new string. The changed string is ║ ║ returned. If the haystack doesn't contain the old string, the ║ ║ original haystack is returned. If the old string is a null string, ║ ║ then the original string is prefixed with the new string. ║ ║ ║ ║ new string to be used►──────────┐ ┌─────◄limit of # changes (times).║ ║ original string (haystack)►──────┐ │ │ [default: ≈ one billion]║ ║ old string to be replaced►──┐ │ │ │ ┌────◄begin at this occurrence #║ ║ {O, H, and N can be null.} │ │ │ │ │ ┌──◄start position (default=1)║ ╚═╦════════════════════════════╗ │ │ │ │ │ │ ╔═════════════════════════╦═╝

 ╚════════════════════════════╝ │ │ │ │ │ │ ╚═════════════════════════╝
                                ↓ ↓ ↓ ↓ ↓ ↓                            */

changestr: parse arg o,h,n,t,b,p,$ f /*T,B,P are optional.*/ t=word(t 999999999 , 1) /*maybe use the default? */ b=word(b 1 , 1) /* " " " " */ p=word(p 1 , 1) /* " " " " */ if arg() < 3 then signal syntax /*not enough arguments. */ if arg() > 6 then signal syntax /*too many arguments. */ if \datatype(t,'W') then signal syntax /*4th arg not an integer. */ if \datatype(b,'W') then signal syntax /*5th " " " " */ if \datatype(p,'W') then signal syntax /*5th arg " " " */ if t<0 then signal syntax /*4th arg not non-negative*/ if b<1 then signal syntax /*5th arg not positive. */ if p<1 then signal syntax /*6th " " " */ L=length(o) /*length of OLD string. */ if L==0 & t\=0 then return n || h /*changing a null char? */ if p\=1 then do /*if P ¬= 1, adjust F & H.*/

             f=left(h, min(p-1, length(h)))  /*keep first part intact. */
             h=substr(h,p)                   /*only use this part of H.*/
             end                             /*now, proceed as usual.  */
  1. =0 /*# of changed occurrences*/
        do j=1   while  # < t                /*keep changing, T times. */
        parse var  h y  (o)  _ +(L) h        /*parse the haystack ···  */
        if _== then return f || $ || y     /*no more left,  return.  */
        $=$ || y                             /*append the residual txt.*/
        if j<b   then $=$ || o               /*append OLD if too soon. */
                 else do                     /*met the occurrence test.*/
                      $=$ || n               /*append the  NEW  string.*/
                      #=#+1                  /*bump  occurrence number.*/
                      end
        end   /*j*/                          /*Note:  most REXX  ···   */
                                             /* CHANGESTR BIFs only ···*/

return f || $ || h /* support three options. */</lang>

REXX: Version 2

Translation of Sudoku#PL/I

<lang rexx> Parse Arg g.0fid

 Select
   When g.0fid='?' Then Do
     Say 'This program solves any (valid) SUDOKU puzzle'
     Say 'Specify the name of the file containing the puzzle as argument'
     Exit
     End
   When g.0fid= Then
     Call exit 'no input specified'
   When lines(g.0fid)=0 Then
     Call exit 'specified input does not exist'
   Otherwise
     Nop
   End
 instr=
 Do While lines(g.0fid)>0
   instr=instr||linein(g.0fid)
   End
 Call lineout g.0fid
 digits='123456789'
 buffer=translate(instr,digits'000',digits'0.x'||xrange('00'x,'ff'x))
 buffer=space(buffer,0)
 If length(buffer)<>81 Then
   Call exit 'invalid input from file' g.0fid
 Call set_geometry
 posbit.=copies('0',9)
 z=posbit.0
 d.z=0
 Do i=1 To 9
   posbit.i=overlay('1',posbit.i,i,1)
   z=posbit.i
   d.z=i
   End
 Do r=1 To 9
   Do c=1 To 9
     Parse Var buffer d +1 buffer
     matrix.r.c=posbit.d
     End
   End
 nn=0
 Call show_matrix 'input from' g.0fid
 res=solve()
 If res Then Do
   Call dbg 'nn='format(nn,5) 'res='res
   Call show_matrix 'solution'
   End
 Else
   Say 'impossible'
 Exit

solve: Procedure Expose g. matrix. posbit. nn box. boxlr. boxlc.

 nn=nn+1
 Call dbg 'solve nn='format(nn,5)
 do i = 1 to 9
   do j = 1 to 9
     if matrix.i.j=posbit.0 Then
       Leave i
     End
   End
 If i>9 Then Do
   do i = 1 to 9
     do j = 1 to 9
       k = pos('1',matrix.i.j)
       Call dbg 'sudoku',
                      Format(nn,9) Format(i,9) Format(j,9) Format(k,9)
       matrix.i.j=posbit.0
       result_=neg(or(any_col(i),any_row(j),any_box(i,j)))
       If substr(result_,k,1)=0 Then
         Return 0
       matrix.i.j=posbit.k
       End
     End
   Return 1
   End
 Else Do
   result_=neg(or(any_col(i),any_row(j),any_box(i,j)))
   Call dbg 'resulta='result_
   k=0;
   do Until k=0
     Call dbg 'resultb='result_
     k=pos('1',result_,k+1)
     Call dbg 'k='Format(k,2)Format(i,2)Format(j,2)
     if k>0 then Do;
       matrix.i.j=posbit.k
       Call dbg 'setting matrix('i','j')->'k
       res=solve()
       Call dbg 'A nn='format(nn,5) 'res='res
       if res then
         return 1
       else Do;
         matrix.i.j=posbit.0
         Call dbg 'setting matrix('i','j')->'0
         End;
       end;
     end;
   return 0
   end;

set_geometry:

 box.=
 Do j=1 To 9                       /* build the box bounds.         */
   rr=(((j*3)%10)+1)*3-2           /* compute row lower bound.      */
   cc=(((j-1)//3)+1)*3-2           /* compute col lower bound.      */
   boxr.j=rr
   boxc.j=cc
   Do r=rr To rr+2                 /* build boxes with cell #s.     */
     Do c=cc To cc+2
       box.r.c=j
       End
     End
   End                             /* j                             */
 rowlb.=10                         /* row R,  low box number=b.     */
 collb.=10                         /* col R,  low box number=b.     */
 boxlr.=10                         /* box B,  low row number=r.     */
 boxlc.=10                         /* box B,  low col number=c.     */
 Do r=1 To 9
   Do c=1 To 9
     b=box.r.c                     /* what box is this R,C in ?     */
     rowlb.r=min(rowlb.r,b)        /* find min box # for row R.     */
     collb.c=min(collb.c,b)        /* find min box # for col C.     */
     boxlr.b=min(boxlr.b,r)        /* find min row # for box B.     */
     boxlc.b=min(boxlc.b,c)        /* find min col # for box B.     */
     End
   End

Return

any_col: Procedure Expose matrix.

 Parse Arg r
 res='000000000'
 Do c=1 To 9
   p=pos('1',matrix.r.c)
   If p>0 Then
     res=overlay('1',res,p,1)
   End
 Return res

any_row: Procedure Expose matrix.

 Parse Arg c
 res='000000000'
 Do r=1 To 9
   p=pos('1',matrix.r.c)
   If p>0 Then
     res=overlay('1',res,p,1)
   End
 Return res

any_box: Procedure Expose matrix. box. boxlr. boxlc.

 Parse Arg r,c
 b=box.r.c
 res='000000000'
 Do r=boxlr.b For 3
   Do c=boxlc.b For 3
     p=pos('1',matrix.r.c)
     If p>0 Then
       res=overlay('1',res,p,1)
     End
   End
 Return res

or: Procedure

 res='000000000'
 Do ia=1 To 3
   a=arg(ia)
   Do p=1 To 9
     If substr(a,p,1)=1 Then
       res=overlay('1',res,p,1)
     End
   End
 Return res

neg: Procedure

 Parse Arg s
 res=
 Do p=1 To 9
   If substr(s,p,1)=1 Then
     res=res'0'
   Else
     res=res'1'
   End
 Return res

o: Say arg(1)

  Return

show_matrix:

 Call o arg(1)
 Do r=1 To 9
   ol=
   Do c=1 To 9
     m=matrix.r.c
     ol=ol||d.m' '
     If c//3=0 Then
       ol=ol' '
     End
   Call o ol
   If r//3=0 Then
     Call o ' '
   End
 Return

dbg:

 If debug=1 Then
   Say arg(1)
 Return

exit: Say '*ERROR*' arg(1)</lang>

Output:
input from d:\_sudoku\in\sdk001.in
4 6 0  0 0 1  0 0 0
0 0 2  0 9 6  0 0 0
0 3 0  0 0 0  0 6 8

0 0 0  0 0 0  0 3 7
0 0 0  6 0 7  0 0 0
5 1 0  0 0 0  0 0 0

8 4 0  0 0 0  0 5 0
0 0 0  7 1 0  9 0 0
0 0 0  3 0 0  0 2 4

solution
4 6 5  8 3 1  2 7 9
7 8 2  4 9 6  3 1 5
1 3 9  5 7 2  4 6 8

6 9 4  1 2 5  8 3 7
3 2 8  6 4 7  5 9 1
5 1 7  9 8 3  6 4 2

8 4 1  2 6 9  7 5 3
2 5 3  7 1 4  9 8 6
9 7 6  3 5 8  1 2 4

REXX: Version 3