Range expansion

A format for expressing an ordered list of integers is to use a comma separated list of either

individual integers
Or a range of integers denoted by the starting integer separated from the end integer in the range by a dash, '-'. (The range includes all integers in the interval including both endpoints)

The range syntax is to be used only for, and for every range that expands to more than two values.

Example
The list of integers:

-6, -3, -2, -1, 0, 1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20

Is accurately expressed by the range expression:

-6,-3-1,3-5,7-11,14,15,17-20

(And vice-versa).

The task

Expand the range description:

-6,-3--1,3-5,7-11,14,15,17-20

Note that the second element above, is the range from minus 3 to minus 1.

C.f. Range extraction

Ada

The function Expand takes a string and returns a corresponding array of integers. Upon syntax errors Constraint_Error is propagated: <lang Ada>with Ada.Text_IO; use Ada.Text_IO; procedure Test_Range_Expansion is

  type Sequence is array (Positive range <>) of Integer;
  function Expand (Text : String) return Sequence is
     To    : Integer := Text'First;
     Count : Natural := 0;
     Low   : Integer;
     function Get return Integer is
        From : Integer := To;
     begin
        if Text (To) = '-' then
           To := To + 1;
        end if;
        while To <= Text'Last loop
           case Text (To) is
              when ',' | '-' => exit;
              when others => To := To + 1;
           end case;
        end loop;
        return Integer'Value (Text (From..To - 1));
     end Get;
  begin
     while To <= Text'Last loop -- Counting items of the list
        Low := Get;
        if To > Text'Last or else Text (To) = ',' then
           Count := Count + 1;
        else
           To := To + 1;
           Count := Count + Get - Low + 1;
        end if;
        To := To + 1;
     end loop;
     return Result : Sequence (1..Count) do
        Count := 0;
        To := Text'First;
        while To <= Text'Last loop -- Filling the list
           Low := Get;
           if To > Text'Last or else Text (To) = ',' then
              Count := Count + 1;
              Result (Count) := Low;
           else
              To := To + 1;
              for Item in Low..Get loop
                 Count := Count + 1;
                 Result (Count) := Item;
              end loop;
           end if;
           To := To + 1;
        end loop;
     end return;
  end Expand;
  procedure Put (S : Sequence) is
     First : Boolean := True;
  begin
     for I in S'Range loop
        if First then
           First := False;
        else
           Put (',');
        end if;
        Put (Integer'Image (S (I)));
     end loop;
  end Put;

begin

  Put (Expand ("-6,-3--1,3-5,7-11,14,15,17-20"));

end Test_Range_Expansion;</lang>

Output:

-6,-3,-2,-1, 3, 4, 5, 7, 8, 9, 10, 11, 14, 15, 17, 18, 19, 20

ALGOL 68

This example is incorrect. Please fix the code and remove this message.

Details: The task example was modified after discussion in the talk page.

Works with: ALGOL 68 version Revision 1 - no extensions to language used

Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny

Works with: ELLA ALGOL 68 version Any (with appropriate job cards) - tested with release 1.8-8d

<lang algol68>MODE YIELDINT = PROC(INT)VOID;

MODE RANGE = STRUCT(INT lwb, upb); MODE RANGEINT = UNION(RANGE, INT);

OP SIZEOF = ([]RANGEINT list)INT: (

determine the length of the output array #

 INT upb := LWB list - 1;
 FOR key FROM LWB list TO UPB list DO
   CASE list[key] IN
     (RANGE value): upb +:= upb OF value - lwb OF value + 1,
     (INT): upb +:= 1
   ESAC
 OD;
 upb

);

PROC gen range expand = ([]RANGEINT list, YIELDINT yield)VOID:

 FOR key FROM LWB list TO UPB list DO
   CASE list[key] IN
     (RANGE range): FOR value FROM lwb OF range TO upb OF range DO yield(value) OD,
     (INT int): yield(int)
   ESAC
 OD;

PROC range expand = ([]RANGEINT list)[]INT: (

 [LWB list: LWB list + SIZEOF list - 1]INT out;
 INT upb := LWB out - 1;

FOR INT value IN # gen range expand(list, # ) DO #
1. (INT value)VOID:

   out[upb +:= 1] := value

OD #);

out

);

test:(

 []RANGEINT list = (-6, RANGE(-3, -1), RANGE(3, 5),  RANGE(7, 11), 14, 15, RANGE(17, 20));
 print((range expand(list), new line))

)</lang>

Output:

         -6         -3         -2         -1         +3         +4         +5         +7         +8         +9        +10        +11        +14        +15        +17        +18        +19        +20

AutoHotkey

<lang AutoHotkey>msgbox % expand("-6,-3--1,3-5,7-11,14,15,17-20")

expand( range ) {

   p := 0
   while p := RegExMatch(range, "\s*(-?\d++)(?:\s*-\s*(-?\d++))?", f, p+1+StrLen(f))
       loop % (f2 ? f2-f1 : 0) + 1
           ret .= "," (A_Index-1) + f1
   return SubStr(ret, 2)

}</lang>

BBC BASIC

<lang bbcbasic> PRINT FNrangeexpand("-6,-3--1,3-5,7-11,14,15,17-20")

     END
     
     DEF FNrangeexpand(r$)
     LOCAL i%, j%, k%, t$
     REPEAT
       i% = INSTR(r$, "-", i%+1)
       IF i% THEN
         j% = i%
         WHILE MID$(r$,j%-1,1)<>"," AND j%<>1
           j% -= 1
         ENDWHILE
         IF i%>j% IF MID$(r$,j%,i%-j%)<>STRING$(i%-j%," ") THEN
           t$ = ""
           FOR k% = VALMID$(r$,j%) TO VALMID$(r$,i%+1)-1
             t$ += STR$(k%) + ","
           NEXT
           r$ = LEFT$(r$,j%-1) + t$ + MID$(r$,i%+1)
           i% = j% + LEN(t$) + 2
         ENDIF
       ENDIF
     UNTIL i% = 0
     = r$</lang>

Output:

-6,-3,-2,-1,3,4,5,7,8,9,10,11,14,15,17,18,19,20

Bracmat

<lang bracmat> ( expandRanges

 =   a b L
   .     @( !arg
          :   (#(?a:?b)|#?a "-" #?b)
              (:?L|"," [%(expandRanges$!sjt:?L))
          )
       &   whl
         ' (   (!L:&!b|(!b,!L))
             : ?L
           & -1+!b:~<!a:?b
           )
       & !L
     |
 )

& out$(str$(expandRanges$"-6,-3--1,3-5,7-11,14,15,17-20")) </lang> Output:

-6,-3,-2,-1,3,4,5,7,8,9,10,11,14,15,17,18,19,20

C

Recursive descent parser. <lang c>#include <stdio.h>

include <stdlib.h>
include <ctype.h>

/* BNFesque rangelist := (range | number) [',' rangelist] range := number '-' number */

int get_list(const char *, char **); int get_rnge(const char *, char **);

/* parser only parses; what to do with parsed items is up to

the add_number and and_range functions */

void add_number(int x); int add_range(int x, int y);

define skip_space while(isspace(*s)) s++
define get_number(x, s, e) (x = strtol(s, e, 10), *e != s)

int get_list(const char *s, char **e) { int x; while (1) { skip_space; if (!get_rnge(s, e) && !get_number(x, s, e)) break; s = *e;

skip_space; if ((*s) == '\0') { putchar('\n'); return 1; } if ((*s) == ',') { s++; continue; } break; } *(const char **)e = s; printf("\nSyntax error at %s\n", s); return 0; }

int get_rnge(const char *s, char **e) { int x, y; char *ee; if (!get_number(x, s, &ee)) return 0; s = ee;

skip_space; if (*s != '-') { *(const char **)e = s; return 0; } s++; if(!get_number(y, s, e)) return 0; return add_range(x, y); }

void add_number(int x) { printf("%d ", x); }

int add_range(int x, int y) { if (y <= x) return 0; while (x <= y) printf("%d ", x++); return 1; }

int main() { char *end;

/* this is correct */ if (get_list("-6,-3--1,3-5,7-11,14,15,17-20", &end)) puts("Ok");

/* this is not. note the subtle error: "-6 -3" is parsed * as range(-6, 3), so synax error comes after that */ get_list("-6 -3--1,3-5,7-11,14,15,17-20", &end);

return 0; }</lang>

Output:

-6 -3 -2 -1 3 4 5 7 8 9 10 11 14 15 17 18 19 20 
Ok
-6 -5 -4 -3 -2 -1 0 1 2 3 
Syntax error at --1,3-5,7-11,14,15,17-20

C#

Works with: C sharp version 3.0

<lang csharp>using System; using System.Collections.Generic; using System.Linq; using System.Text.RegularExpressions;

class Program {

   static void Main(string[] args)
   {
       var rangeString = "-6,-3--1,3-5,7-11,14,15,17-20";
       var matches = Regex.Matches(rangeString, @"((?<f>-?\d+)-(?-?\d+))|(-?\d+)");

With conventional list processing

With a parser

Icon and Unicon

Spidermonkey version

MATLAB / Octave

version 1

Version 2 somewhat simplified !?!