Execute a Markov algorithm
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You are encouraged to solve this task according to the task description, using any language you may know.
Create an interpreter for a Markov Algorithm. Rules have the syntax:
<ruleset> ::= ((<comment> | <rule>) <newline>+)*
<comment> ::= # {<any character>}
<rule> ::= <pattern> <whitespace> -> <whitespace> [.] <replacement>
<whitespace> ::= (<tab> | <space>) [<whitespace>]
There is one rule per line. If there is a . present before the <replacement>, then this is a terminating rule in which case the interpreter must halt execution. A ruleset consists of a sequence of rules, with optional comments.
Rulesets
Use the following tests on entries:
Ruleset 1
# This rules file is extracted from Wikipedia: # http://en.wikipedia.org/wiki/Markov_Algorithm A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule
Sample text of:
I bought a B of As from T S.
Should generate the output:
I bought a bag of apples from my brother.
Ruleset 2
A test of the terminating rule
# Slightly modified from the rules on Wikipedia A -> apple B -> bag S -> .shop T -> the the shop -> my brother a never used -> .terminating rule
Sample text of:
I bought a B of As from T S.
Should generate:
I bought a bag of apples from T shop.
Ruleset 3
This tests for correct substitution order and may trap simple regexp based replacement routines if special regexp characters are not escaped.
# BNF Syntax testing rules A -> apple WWWW -> with Bgage -> ->.* B -> bag ->.* -> money W -> WW S -> .shop T -> the the shop -> my brother a never used -> .terminating rule
Sample text of:
I bought a B of As W my Bgage from T S.
Should generate:
I bought a bag of apples with my money from T shop.
Ruleset 4
This tests for correct order of scanning of rules, and may trap replacement routines that scan in the wrong order. It implements a general unary multiplication engine. (Note that the input expression must be placed within underscores in this implementation.)
### Unary Multiplication Engine, for testing Markov Algorithm implementations ### By Donal Fellows. # Unary addition engine _+1 -> _1+ 1+1 -> 11+ # Pass for converting from the splitting of multiplication into ordinary # addition 1! -> !1 ,! -> !+ _! -> _ # Unary multiplication by duplicating left side, right side times 1*1 -> x,@y 1x -> xX X, -> 1,1 X1 -> 1X _x -> _X ,x -> ,X y1 -> 1y y_ -> _ # Next phase of applying 1@1 -> x,@y 1@_ -> @_ ,@_ -> !_ ++ -> + # Termination cleanup for addition _1 -> 1 1+_ -> 1 _+_ ->
Sample text of:
_1111*11111_
should generate the output:
11111111111111111111
Ruleset 5
A simple Turing machine, implementing a three-state busy beaver.
The tape consists of 0s and 1s, the states are A, B, C and H (for Halt), and the head position is indicated by writing the state letter before the character where the head is. All parts of the initial tape the machine operates on have to be given in the input.
Besides demonstrating that the Markov algorithm is Turing-complete, it also made me catch a bug in the C++ implementation which wasn't caught by the first four rulesets.
# Turing machine: three-state busy beaver # # state A, symbol 0 => write 1, move right, new state B A0 -> 1B # state A, symbol 1 => write 1, move left, new state C 0A1 -> C01 1A1 -> C11 # state B, symbol 0 => write 1, move left, new state A 0B0 -> A01 1B0 -> A11 # state B, symbol 1 => write 1, move right, new state B B1 -> 1B # state C, symbol 0 => write 1, move left, new state B 0C0 -> B01 1C0 -> B11 # state C, symbol 1 => write 1, move left, halt 0C1 -> H01 1C1 -> H11
This ruleset should turn
000000A000000
into
00011H1111000
Examples
Ada
markov.ads: <lang Ada>with Ada.Strings.Unbounded;
package Markov is
use Ada.Strings.Unbounded; type Ruleset (Length : Natural) is private; type String_Array is array (Positive range <>) of Unbounded_String; function Parse (S : String_Array) return Ruleset; function Apply (R : Ruleset; S : String) return String;
private
type Entry_Kind is (Comment, Rule);
type Set_Entry (Kind : Entry_Kind := Rule) is record
case Kind is
when Rule =>
Source : Unbounded_String;
Target : Unbounded_String;
Is_Terminating : Boolean;
when Comment =>
Text : Unbounded_String;
end case;
end record;
subtype Rule_Entry is Set_Entry (Kind => Rule);
type Entry_Array is array (Positive range <>) of Set_Entry;
type Ruleset (Length : Natural) is record
Entries : Entry_Array (1 .. Length);
end record;
end Markov;</lang>
markov.adb: <lang Ada>package body Markov is
function Parse (S : String_Array) return Ruleset is
Result : Ruleset (Length => S'Length);
begin
for I in S'Range loop
if Length (S (I)) = 0 or else Element (S (I), 1) = '#' then
Result.Entries (I) := (Kind => Comment, Text => S (I));
else
declare
Separator : Natural;
Terminating : Boolean;
Target : Unbounded_String;
begin
Separator := Index (S (I), " -> ");
if Separator = 0 then
raise Constraint_Error;
end if;
Target :=
Unbounded_Slice
(Source => S (I),
Low => Separator + 4,
High => Length (S (I)));
Terminating := Length (Target) > 0
and then Element (Target, 1) = '.';
if Terminating then
Delete (Source => Target, From => 1, Through => 1);
end if;
Result.Entries (I) :=
(Kind => Rule,
Source => Unbounded_Slice
(Source => S (I),
Low => 1,
High => Separator - 1),
Target => Target,
Is_Terminating => Terminating);
end;
end if;
end loop;
return Result;
end Parse;
procedure Apply
(R : Rule_Entry;
S : in out Unbounded_String;
Modified : in out Boolean)
is
Pattern : String := To_String (R.Source);
Where : Natural := Index (S, Pattern);
begin
while Where /= 0 loop
Modified := True;
Replace_Slice
(Source => S,
Low => Where,
High => Where + Pattern'Length - 1,
By => To_String (R.Target));
Where := Index (S, Pattern, Where + Length (R.Target));
end loop;
end Apply;
function Apply (R : Ruleset; S : String) return String is
Result : Unbounded_String := To_Unbounded_String (S);
Current_Rule : Set_Entry;
Modified : Boolean := False;
begin
loop
Modified := False;
for I in R.Entries'Range loop
Current_Rule := R.Entries (I);
if Current_Rule.Kind = Rule then
Apply (Current_Rule, Result, Modified);
exit when Current_Rule.Is_Terminating or else Modified;
end if;
end loop;
exit when not Modified;
end loop;
return To_String (Result);
end Apply;
end Markov;</lang>
test_markov.adb: <lang Ada>with Ada.Command_Line; with Ada.Text_IO.Unbounded_IO; with Ada.Strings.Unbounded; with Markov;
procedure Test_Markov is
use Ada.Strings.Unbounded; package IO renames Ada.Text_IO.Unbounded_IO; Rule_File : Ada.Text_IO.File_Type; Line_Count : Natural := 0;
begin
if Ada.Command_Line.Argument_Count /= 2 then
Ada.Text_IO.Put_Line ("Usage: test_markov ruleset_file source_file");
return;
end if;
Ada.Text_IO.Open
(File => Rule_File,
Mode => Ada.Text_IO.In_File,
Name => Ada.Command_Line.Argument (1));
while not Ada.Text_IO.End_Of_File (Rule_File) loop
Ada.Text_IO.Skip_Line (Rule_File);
Line_Count := Line_Count + 1;
end loop;
declare
Lines : Markov.String_Array (1 .. Line_Count);
begin
Ada.Text_IO.Reset (Rule_File);
for I in Lines'Range loop
Lines (I) := IO.Get_Line (Rule_File);
end loop;
Ada.Text_IO.Close (Rule_File);
declare
Ruleset : Markov.Ruleset := Markov.Parse (Lines);
Source_File : Ada.Text_IO.File_Type;
begin
Ada.Text_IO.Open
(File => Source_File,
Mode => Ada.Text_IO.In_File,
Name => Ada.Command_Line.Argument (2));
while not Ada.Text_IO.End_Of_File (Source_File) loop
Ada.Text_IO.Put_Line
(Markov.Apply (Ruleset, Ada.Text_IO.Get_Line (Source_File)));
end loop;
Ada.Text_IO.Close (Source_File);
end;
end;
end Test_Markov;</lang>
Output (rulesX contains the ruleset of above examples and testX the example text):
$ ./test_markov rules1 test1 I bought a bag of apples from my brother. $ ./test_markov rules2 test2 I bought a bag of apples from T shop. $ ./test_markov rules3 test3 I bought a bag of apples with my money from T shop. $ ./test_markov rules4 test4 11111111111111111111 $ ./test_markov rules5 test5 00011H1111000
AutoHotkey
<lang autohotkey>;---------------------------------------------------------------------------
- Markov Algorithm.ahk
- by wolf_II
- ---------------------------------------------------------------------------
- interpreter for a Markov Algorithm
- ---------------------------------------------------------------------------
- ---------------------------------------------------------------------------
AutoExecute: ; auto-execute section of the script
- ---------------------------------------------------------------------------
#SingleInstance, Force ; only one instance allowed #NoEnv ; don't check empty variables StartupDir := A_WorkingDir ; remember startup directory SetWorkingDir, %A_ScriptDir% ; change directoy StringCaseSense, On ; case sensitive comparisons ;----------------------------------------------------------------------- AppName := "Markov Algorithm" Gosub, GuiCreate Gui, Show,, %AppName%
Return
- ---------------------------------------------------------------------------
GuiCreate: ; create the GUI
- ---------------------------------------------------------------------------
; GUI options Gui, -MinimizeBox Gui, Add, Edit, y0 h0 ; catch the focus
; Ruleset Gui, Add, GroupBox, w445 h145 Section, Ruleset Gui, Add, Edit, xs+15 ys+20 w300 r8 vRuleset Gui, Add, Button, x+15 w100, Load Ruleset Gui, Add, Button, wp, Save Ruleset Gui, Add, Button, w30, 1 Gui, Add, Button, x+5 wp, 2 Gui, Add, Button, x+5 wp, 3 Gui, Add, Button, xs+330 y+6 wp, 4 Gui, Add, Button, x+5 wp, 5
; String Gui, Add, GroupBox, xs w445 h75 Section, String Gui, Add, Edit, xs+15 ys+20 w300 vString Gui, Add, Button, x+15 w100, Apply Ruleset Gui, Add, Button, xp wp Hidden, Stop Gui, Add, CheckBox, xs+15 yp+30 vSingleStepping, Single Stepping?
; Output Gui, Add, GroupBox, xs w445 h235 Section, Output Gui, Add, Edit, xs+15 ys+20 w415 r15 ReadOnly vOutput HwndhOut
Return
- ---------------------------------------------------------------------------
GuiClose:
- ---------------------------------------------------------------------------
ExitApp
Return
- ---------------------------------------------------------------------------
ButtonLoadRuleset: ; load ruleset from file
- ---------------------------------------------------------------------------
Gui, +OwnDialogs
FileSelectFile, RulesetFile,,, Load Ruleset, *.markov
If Not SubStr(RulesetFile, -6) = ".markov"
RulesetFile .= ".markov"
If FileExist(RulesetFile) {
FileRead, Ruleset, %RulesetFile%
GuiControl,, Ruleset, %Ruleset%
} Else
MsgBox, 16, Error - %AppName%, File not found:`n`n"%RulesetFile%"
Return
- ---------------------------------------------------------------------------
ButtonSaveRuleset: ; save ruleset to file
- ---------------------------------------------------------------------------
Gui, +OwnDialogs
Gui, Submit, NoHide
FileSelectFile, RulesetFile, S16,, Save Ruleset, *.markov
If Not SubStr(RulesetFile, -6) = ".markov"
RulesetFile .= ".markov"
FileDelete, %RulesetFile%
FileAppend, %Ruleset%, %RulesetFile%
Gui, Show
Return
_
- ---------------------------------------------------------------------------
Button1: ; http://rosettacode.org/wiki/Execute_a_Markov_algorithm#Ruleset_1
- ---------------------------------------------------------------------------
GuiControl,, Output ; clear output GuiControl,, String, I bought a B of As from T S. GuiControl,, Ruleset, (LTrim # This rules file is extracted from Wikipedia: # http://en.wikipedia.org/wiki/Markov_Algorithm A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule )
Return
- ---------------------------------------------------------------------------
Button2: ; http://rosettacode.org/wiki/Execute_a_Markov_algorithm#Ruleset_2
- ---------------------------------------------------------------------------
GuiControl,, Output ; clear output GuiControl,, String, I bought a B of As from T S. GuiControl,, Ruleset, (LTrim # Slightly modified from the rules on Wikipedia A -> apple B -> bag S -> .shop T -> the the shop -> my brother a never used -> .terminating rule )
Return
- ---------------------------------------------------------------------------
Button3: ; http://rosettacode.org/wiki/Execute_a_Markov_algorithm#Ruleset_3
- ---------------------------------------------------------------------------
GuiControl,, Output ; clear output GuiControl,, String, I bought a B of As W my Bgage from T S. GuiControl,, Ruleset, (LTrim # BNF Syntax testing rules A -> apple WWWW -> with Bgage -> ->.* B -> bag ->.* -> money W -> WW S -> .shop T -> the the shop -> my brother a never used -> .terminating rule )
Return
- ---------------------------------------------------------------------------
Button4: ; http://rosettacode.org/wiki/Execute_a_Markov_algorithm#Ruleset_4
- ---------------------------------------------------------------------------
GuiControl,, Output ; clear output GuiControl,, String, _1111*11111_ GuiControl,, Ruleset, (LTrim ### Unary Multiplication Engine, for testing Markov Algorithm implementations ### By Donal Fellows. # Unary addition engine _+1 -> _1+ 1+1 -> 11+ # Pass for converting from the splitting of multiplication into ordinary # addition 1! -> !1 ,! -> !+ _! -> _ # Unary multiplication by duplicating left side, right side times 1*1 -> x,@y 1x -> xX X, -> 1,1 X1 -> 1X _x -> _X ,x -> ,X y1 -> 1y y_ -> _ # Next phase of applying 1@1 -> x,@y 1@_ -> @_ ,@_ -> !_ ++ -> + # Termination cleanup for addition _1 -> 1 1+_ -> 1 _+_ -> )
Return
- ---------------------------------------------------------------------------
Button5: ; http://rosettacode.org/wiki/Execute_a_Markov_algorithm#Ruleset_5
- ---------------------------------------------------------------------------
GuiControl,, Output ; clear output GuiControl,, String, 000000A000000 GuiControl,, Ruleset, (LTrim # Turing machine: three-state busy beaver # # state A, symbol 0 => write 1, move right, new state B A0 -> 1B # state A, symbol 1 => write 1, move left, new state C 0A1 -> C01 1A1 -> C11 # state B, symbol 0 => write 1, move left, new state A 0B0 -> A01 1B0 -> A11 # state B, symbol 1 => write 1, move right, new state B B1 -> 1B # state C, symbol 0 => write 1, move left, new state B 0C0 -> B01 1C0 -> B11 # state C, symbol 1 => write 1, move left, halt 0C1 -> H01 1C1 -> H11 )
Return
- ---------------------------------------------------------------------------
ButtonApplyRuleset: ; flow control for Algorithm
- ---------------------------------------------------------------------------
; prepare Gui, Submit, NoHide GuiControl,, Output ; clear Controls(False) ; disable Count := 0 Subst := True Stop := False
; keep substituting for as long as necessary
While, Subst {
Subst := False ; reset control variable
IfEqual, Stop, 1, Break
Gosub, Algorithm
}
; clean up
Output("Substitution count: " Count)
Controls(True) ; re-enable
Return
- ---------------------------------------------------------------------------
ButtonStop: ; this button is initially hidden
- ---------------------------------------------------------------------------
Stop := True
Return
- ---------------------------------------------------------------------------
Algorithm: ; http://rosettacode.org/wiki/Execute_a_Markov_algorithm
- ---------------------------------------------------------------------------
; Parse the ruleset and apply each rule to the string. Whenever a rule
; has changed the string goto first rule. Continue until a encountering
; a terminating rule, or until no further changes to the strings are
; made.
;-----------------------------------------------------------------------
Loop, Parse, Ruleset, `n, `r ; always start from the beginning
{
; check for comment
If SubStr(A_LoopField, 1, 1) = "#"
Continue ; get next line
; split a rule into $Search, $Terminator and $Replace
LookFor := "(?P<Search>.+) -> (?P<Terminator>\.?)(?P<Replace>.+)"
RegExMatch(A_LoopField, LookFor, $)
; single stepping through possible substitutions
If SingleStepping
MsgBox,, %AppName%, % ""
. "Rule = """ A_LoopField """`n`n"
. "Search`t= """ $Search """`n"
. "Replace`t= """ $Replace """`n"
. "Termintor`t= """ ($Terminator ? "True" : "False") """`n"
; try to substitute
StringReplace, String, String, %$Search%, %$Replace%, UseErrorLevel
; any success?
If ErrorLevel { ; yes, substitution done
Count++ ; keep count
Subst := True ; set control variable
Output(String) ; write new string to output
}
; terminate?
If $Terminator { ; yes, terminate
Stop := True ; set control variable
Break ; back to flow control
}
; we are not yet terminated ...
If Subst ; but we just did a substitution
Break ; back to flow control
}
Return
- ---------------------------------------------------------------------------
Controls(Bool) { ; [en|dis]able controls
- ---------------------------------------------------------------------------
Enable := Bool ? "+" : "-"
Disable := Bool ? "-" : "+"
Loop, 2
GuiControl, %Disable%ReadOnly, % "Edit" A_Index + 1
Loop, 7
GuiControl, %Disable%Disabled, % "Button" A_Index + 1
GuiControl, %Disable%Disabled, Edit4
GuiControl, %Disable%Hidden, Button10
GuiControl, %Enable%Hidden, Button11
GuiControl, %Disable%Disabled, Button12
}
- ---------------------------------------------------------------------------
Output(Text) { ; append text to output
- ---------------------------------------------------------------------------
static EM_REPLACESEL = 0xC2 global hOut Sleep, 100 Text .= "`r`n" SendMessage, EM_REPLACESEL,, &Text,, ahk_id %hOut%
}
- ---------- end of file ----------------------------------------------------</lang>
BBC BASIC
<lang bbcbasic> PRINT FNmarkov("ruleset1.txt", "I bought a B of As from T S.")
PRINT FNmarkov("ruleset2.txt", "I bought a B of As from T S.")
PRINT FNmarkov("ruleset3.txt", "I bought a B of As W my Bgage from T S.")
PRINT FNmarkov("ruleset4.txt", "_1111*11111_")
PRINT FNmarkov("ruleset5.txt", "000000A000000")
END
DEF FNmarkov(rulefile$, text$)
LOCAL i%, done%, rules%, rule$, old$, new$
rules% = OPENIN(rulefile$)
IF rules%=0 ERROR 100, "Cannot open rules file"
REPEAT
rule$ = GET$#rules%
IF ASC(rule$)<>35 THEN
REPEAT
i% = INSTR(rule$, CHR$(9))
IF i% MID$(rule$,i%,1) = " "
UNTIL i%=0
i% = INSTR(rule$, " -> ")
IF i% THEN
old$ = LEFT$(rule$,i%-1)
WHILE RIGHT$(old$)=" " old$ = LEFT$(old$) : ENDWHILE
new$ = MID$(rule$,i%+4)
WHILE ASC(new$)=32 new$ = MID$(new$,2) : ENDWHILE
IF ASC(new$)=46 new$ = MID$(new$,2) : done% = TRUE
i% = INSTR(text$,old$)
IF i% THEN
text$ = LEFT$(text$,i%-1) + new$ + MID$(text$,i%+LEN(old$))
PTR#rules% = 0
ENDIF
ENDIF
ENDIF
UNTIL EOF#rules% OR done%
CLOSE #rules%
= text$</lang>
Output:
I bought a bag of apples from my brother. I bought a bag of apples from T shop. I bought a bag of apples with my money from T shop. 11111111111111111111 00011H1111000
Bracmat
Save the following text to a file "markov.bra": <lang bracmat> markov= { First the patterns that describe the rules syntax. This is a naive and not very efficient way to parse the rules, but it closely matches the problem description, which is nice. }
( ruleset
= >%@" " ? { Added: assume that a rule cannot start with whitespace.
The %@ say that the thing to match must be exactly one
byte. % means 'one or more'. @ means 'zero or one'.
}
: ((!comment|!rule) !newlines) !ruleset
| { Recursion terminates here: match empty string. }
)
& (comment="#" ?com)
& ( rule
= %?pattern
!whitespace
"->"
!whitespace
( "." %?replacement&stop:?stop
| %?replacement
)
)
& ( whitespace
= (\t|" ") (!whitespace|)
)
& ( newlines
= ( (\n|\r)
& ( :!pattern:!replacement {Do nothing. We matched an empty line.}
| (!pattern.!replacement.!stop) !rules:?rules
{
Add pattern, replacement and the stop (empty string or "stop")
to a list of triplets. This list will contain the rules in
reverse order.
Then, reset these variables, so they are not added once more
if an empty line follows.
}
& :?stop:?pattern:?replacement
)
)
(!newlines|)
)
{ Compile the textual rules to a single Bracmat pattern. }
& ( compileRules
= stop pattern replacement rules,pat rep stp
. :?stop:?pattern:?replacement:?rules
{
Important! Initialise these variables.
}
& @(!arg:!ruleset)
{
That's all. The textual rules are parsed and converted to a
list of triplets. The rules in the list are in reversed order.
}
& !rules:(?pat.?rep.?stp) ?rules
{
The head of the list is the last rule. Use it to initialise
the pattern "ruleSetAsPattern".
The single quote introduces a macro substition. All symbols
preceded with a $ are substituted.
}
&
' ( ?A ()$pat ?Z
& $stp:?stop
& $rep:?replacement
)
: (=?ruleSetAsPattern)
{
Add all remaining rules as new subpatterns to
"ruleSetAsPattern". Separate with the OR symbol.
}
& whl
' ( !rules:(?pat.?rep.?stp) ?rules
&
' ( ?A ()$pat ?Z
& $stp:?stop
& $rep:?replacement
| $ruleSetAsPattern
)
: (=?ruleSetAsPattern)
)
& '$ruleSetAsPattern
)
{
Function that takes two arguments: a rule set (as text)
and a subject string.
The function returns the transformed string.
}
& ( applyRules
= rulesSetAsText subject ruleSetAsPattern
, A Z replacement stop
. !arg:(?rulesSetAsText.?subject)
& compileRules$!rulesSetAsText:(=?ruleSetAsPattern)
{
Apply rule until no match
or until variable "stop" has been set to the value "stop".
}
& whl
' ( @(!subject:!ruleSetAsPattern)
& str$(!A !replacement !Z):?subject
& !stop:~stop
)
& !subject
)
{ Tests: }
& out
$ ( applyRules
$ ( "# This rules file is extracted from Wikipedia:
A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule "
. "I bought a B of As from T S."
)
)
& out
$ ( applyRules
$ ( "# Slightly modified from the rules on Wikipedia
A -> apple B -> bag S -> .shop T -> the the shop -> my brother a never used -> .terminating rule "
. "I bought a B of As from T S."
)
)
& out
$ ( applyRules
$ ( "# BNF Syntax testing rules
A -> apple WWWW -> with Bgage -> ->.* B -> bag ->.* -> money W -> WW S -> .shop T -> the the shop -> my brother a never used -> .terminating rule "
. "I bought a B of As W my Bgage from T S."
)
)
& out
$ ( applyRules
$ ( "### Unary Multiplication Engine, for testing Markov Algorithm implementations
- By Donal Fellows.
- Unary addition engine
_+1 -> _1+ 1+1 -> 11+
- Pass for converting from the splitting of multiplication into ordinary
- addition
1! -> !1 ,! -> !+ _! -> _
- Unary multiplication by duplicating left side, right side times
1*1 -> x,@y 1x -> xX X, -> 1,1 X1 -> 1X _x -> _X ,x -> ,X y1 -> 1y y_ -> _
- Next phase of applying
1@1 -> x,@y 1@_ -> @_ ,@_ -> !_ ++ -> +
- Termination cleanup for addition
_1 -> 1 1+_ -> 1 _+_ -> "
. "_1111*11111_"
)
)
& out
$ ( applyRules
$ ( "# Turing machine: three-state busy beaver
- state A, symbol 0 => write 1, move right, new state B
A0 -> 1B
- state A, symbol 1 => write 1, move left, new state C
0A1 -> C01 1A1 -> C11
- state B, symbol 0 => write 1, move left, new state A
0B0 -> A01 1B0 -> A11
- state B, symbol 1 => write 1, move right, new state B
B1 -> 1B
- state C, symbol 0 => write 1, move left, new state B
0C0 -> B01 1C0 -> B11
- state C, symbol 1 => write 1, move left, halt
0C1 -> H01 1C1 -> H11 "
. 000000A000000
)
)
& ok
| failure; </lang>
Test:
{?} get$"markov.bra"
{!} markov
S 0,01 sec
{?} !markov
I bought a bag of apples from my brother.
I bought a bag of apples from T shop.
I bought a bag of apples with my money from T shop.
11111111111111111111
00011H1111000
{!} ok
S 0,41 sec
C
<lang c>#include <stdio.h>
- include <stdlib.h>
- include <string.h>
- include <unistd.h>
- include <fcntl.h>
- include <sys/types.h>
- include <sys/stat.h>
- include <ctype.h>
typedef struct { char * s; size_t alloc_len; } string;
typedef struct { char *pat, *repl; int terminate; } rule_t;
typedef struct { int n; rule_t *rules; char *buf; } ruleset_t;
void ruleset_del(ruleset_t *r) { if (r->rules) free(r->rules); if (r->buf) free(r->buf); free(r); }
string * str_new(const char *s) { int l = strlen(s); string *str = malloc(sizeof(string)); str->s = malloc(l + 1); strcpy(str->s, s); str->alloc_len = l + 1; return str; }
void str_append(string *str, const char *s, int len) { int l = strlen(str->s); if (len == -1) len = strlen(s);
if (str->alloc_len < l + len + 1) { str->alloc_len = l + len + 1; str->s = realloc(str->s, str->alloc_len); } memcpy(str->s + l, s, len); str->s[l + len] = '\0'; }
/* swap content of dest and src, and truncate src string */ void str_transfer(string *dest, string *src) { size_t tlen = dest->alloc_len; dest->alloc_len = src->alloc_len; src->alloc_len = tlen;
char *ts = dest->s; dest->s = src->s; src->s = ts; src->s[0] = '\0'; }
void str_del(string *s) { if (s->s) free(s->s); free(s); }
void str_markov(string *str, ruleset_t *r) { int i, j, sl, pl; int changed = 0, done = 0; string *tmp = str_new("");
while (!done) { changed = 0; for (i = 0; !done && !changed && i < r->n; i++) { pl = strlen(r->rules[i].pat); sl = strlen(str->s); for (j = 0; j < sl; j++) { if (strncmp(str->s + j, r->rules[i].pat, pl)) continue; str_append(tmp, str->s, j); str_append(tmp, r->rules[i].repl, -1); str_append(tmp, str->s + j + pl, -1);
str_transfer(str, tmp); changed = 1;
if (r->rules[i].terminate) done = 1; break; } } if (!changed) break; } str_del(tmp); return; }
ruleset_t* read_rules(const char *name) { struct stat s; char *buf; size_t i, j, k, tmp; rule_t *rules = 0; int n = 0; /* number of rules */
int fd = open(name, O_RDONLY); if (fd == -1) return 0;
fstat(fd, &s); buf = malloc(s.st_size + 2); read(fd, buf, s.st_size); buf[s.st_size] = '\n'; buf[s.st_size + 1] = '\0'; close(fd);
for (i = j = 0; buf[i] != '\0'; i++) { if (buf[i] != '\n') continue;
/* skip comments */ if (buf[j] == '#' || i == j) { j = i + 1; continue; }
/* find the '->' */ for (k = j + 1; k < i - 3; k++) if (isspace(buf[k]) && !strncmp(buf + k + 1, "->", 2)) break;
if (k >= i - 3) { printf("parse error: no -> in %.*s\n", i - j, buf + j); break; }
/* left side: backtrack through whitespaces */ for (tmp = k; tmp > j && isspace(buf[--tmp]); ); if (tmp < j) { printf("left side blank? %.*s\n", i - j, buf + j); break; } buf[++tmp] = '\0';
/* right side */ for (k += 3; k < i && isspace(buf[++k]);); buf[i] = '\0';
rules = realloc(rules, sizeof(rule_t) * (1 + n)); rules[n].pat = buf + j;
if (buf[k] == '.') { rules[n].terminate = 1; rules[n].repl = buf + k + 1; } else { rules[n].terminate = 0; rules[n].repl = buf + k; } n++;
j = i + 1; }
ruleset_t *r = malloc(sizeof(ruleset_t)); r->buf = buf; r->rules = rules; r->n = n; return r; }
int test_rules(const char *s, const char *file) { ruleset_t * r = read_rules(file); if (!r) return 0; printf("Rules from '%s' ok\n", file);
string *ss = str_new(s); printf("text: %s\n", ss->s);
str_markov(ss, r); printf("markoved: %s\n", ss->s);
str_del(ss); ruleset_del(r);
return printf("\n"); }
int main() { /* rule 1-5 are files containing rules from page top */ test_rules("I bought a B of As from T S.", "rule1"); test_rules("I bought a B of As from T S.", "rule2"); test_rules("I bought a B of As W my Bgage from T S.", "rule3"); test_rules("_1111*11111_", "rule4"); test_rules("000000A000000", "rule5");
return 0; }</lang>output<lang>Rules from 'rule1' ok text: I bought a B of As from T S. markoved: I bought a bag of apples from my brother.
Rules from 'rule2' ok text: I bought a B of As from T S. markoved: I bought a bag of apples from T shop.
Rules from 'rule3' ok text: I bought a B of As W my Bgage from T S. markoved: I bought a bag of apples with my money from T shop.
Rules from 'rule4' ok text: _1111*11111_ markoved: 11111111111111111111
Rules from 'rule5' ok text: 000000A000000 markoved: 00011H1111000 </lang>
C++
Note: Non-use of iswhite is intentional, since depending on the locale, other chars besides space and tab might be detected by that function.
<lang cpp>
- include <cstdlib>
- include <iostream>
- include <fstream>
- include <vector>
- include <string>
struct rule {
std::string pattern;
std::string replacement;
bool terminal;
rule(std::string pat, std::string rep, bool term):
pattern(pat),
replacement(rep),
terminal(term)
{
}
};
std::string const whitespace = " \t"; std::string::size_type const npos = std::string::npos;
bool is_whitespace(char c) {
return whitespace.find(c) != npos;
}
std::vector<rule> read_rules(std::ifstream& rulefile) {
std::vector<rule> rules;
std::string line;
while (std::getline(rulefile, line))
{
std::string::size_type pos;
// remove comments
pos = line.find('#');
if (pos != npos)
line.resize(pos);
// ignore lines consisting only of whitespace
if (line.find_first_not_of(whitespace) == npos)
continue;
// find "->" surrounded by whitespace
pos = line.find("->");
while (pos != npos && (pos == 0 || !is_whitespace(line[pos-1])))
pos = line.find("->", pos+1);
if (pos == npos || line.length() < pos+3 || !is_whitespace(line[pos+2]))
{
std::cerr << "invalid rule: " << line << "\n";
std::exit(EXIT_FAILURE);
}
std::string pattern = line.substr(0, pos-1);
std::string replacement = line.substr(pos+3);
// remove additional separating whitespace
pattern.erase(pattern.find_last_not_of(whitespace)+1);
replacement.erase(0, replacement.find_first_not_of(whitespace));
// test for terminal rule
bool terminal = !replacement.empty() && replacement[0] == '.';
if (terminal)
replacement.erase(0,1);
rules.push_back(rule(pattern, replacement, terminal));
}
return rules;
}
std::string markov(std::vector<rule> rules, std::string input) {
std::string& output = input; std::vector<rule>::iterator iter = rules.begin();
// Loop through each rule, transforming our current version
// with each rule.
while (iter != rules.end())
{
std::string::size_type pos = output.find(iter->pattern);
if (pos != npos)
{
output.replace(pos, iter->pattern.length(), iter->replacement);
if (iter->terminal)
break;
iter = rules.begin();
}
else
++iter;
}
return output;
}
int main(int argc, char* argv[]) {
if (argc != 3)
{
std::cout << "usage:\n " << argv[0] << " rulefile text\n";
return EXIT_FAILURE;
}
std::ifstream rulefile(argv[1]);
std::vector<rule> rules = read_rules(rulefile);
std::string input(argv[2]); std::string output = markov(rules, input);
std::cout << output << "\n";
}</lang>
Common Lisp
I should mention that this uses the regular expression machinery present in Allegro Lisp but not Common Lisp generally (though there are public domain Lisp libraries). <lang lisp>;;; Keeps track of all our rules (defclass markov ()
((rules :initarg :rules :initform nil :accessor rules)))
- Definition of a rule
(defclass rule ()
((pattern :initarg :pattern :accessor pattern) (replacement :initarg :replacement :accessor replacement) (terminal :initform nil :initarg :terminal :accessor terminal)))
- Parse a rule with this regular expression
(defparameter *rex->* (compile-re "^(.+)(?: |\\t)->(?: |\\t)(\\.?)(.*)$"))
- Create a rule and add it to the markov object
(defmethod update-markov ((mkv markov) lhs terminating rhs)
(setf (rules mkv) (cons
(make-instance 'rule :pattern lhs :replacement rhs :terminal terminating)
(rules mkv))))
- Parse a line and add it to the markov object
(defmethod parse-line ((mkv markov) line)
(let ((trimmed (string-trim #(#\Space #\Tab) line)))
(if (not (or
(eql #\# (aref trimmed 0))
(equal "" trimmed)))
(let ((vals (multiple-value-list (match-re *rex->* line))))
(if (not (car vals))
(progn
(format t "syntax error in ~A" line)
(throw 'fail t)))
(update-markov mkv (nth 2 vals) (equal "." (nth 3 vals)) (nth 4 vals))))))
- Make a markov object from the string of rules
(defun make-markov (rules-text)
(catch 'fail
(let ((mkv (make-instance 'markov)))
(with-input-from-string (s rules-text)
(loop for line = (read-line s nil)
while line do
(parse-line mkv line)))
(setf (rules mkv) (reverse (rules mkv)))
mkv)))
- Given a rule and bounds where it applies, apply it to the input text
(defun adjust (rule-info text)
(let* ((rule (car rule-info))
(index-start (cadr rule-info))
(index-end (caddr rule-info))
(prefix (subseq text 0 index-start))
(suffix (subseq text index-end))
(replace (replacement rule)))
(concatenate 'string prefix replace suffix)))
- Get the next applicable rule or nil if none
(defmethod get-rule ((markov markov) text)
(dolist (rule (rules markov) nil)
(let ((index (search (pattern rule) text)))
(if index
(return (list rule index (+ index (length (pattern rule)))))))))
- Interpret text using a markov object
(defmethod interpret ((markov markov) text)
(let ((rule-info (get-rule markov text))
(ret text))
(loop (if (not rule-info) (return ret))
(setf ret (adjust rule-info ret))
(if (terminal (car rule-info)) (return ret))
(setf rule-info (get-rule markov ret)))))</lang>
Testing: <lang>(defparameter
*rules1*
"# This rules file is extracted from Wikipedia:
A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule")
- Lots of other defparameters for rules omitted here...
(defun test ()
(format t "~A~%" (interpret (make-markov *rules1*) "I bought a B of As from T S.")) (format t "~A~%" (interpret (make-markov *rules2*) "I bought a B of As from T S.")) (format t "~A~%" (interpret (make-markov *rules3*) "I bought a B of As W my Bgage from T S.")) (format t "~A~%" (interpret (make-markov *rules4*) "_1111*11111_")) (format t "~A~%" (interpret (make-markov *rules5*) "000000A000000")) )
(test) I bought a bag of apples from my brother. I bought a bag of apples from T shop. I bought a bag of apples with my money from T shop. 11111111111111111111 00011H1111000 NIL </lang>
D
<lang d>void main() {
import std.stdio, std.file, std.regex, std.string, std.range,
std.functional;
const rules = "markov_rules.txt".readText.splitLines.split("");
auto tests = "markov_tests.txt".readText.splitLines;
auto re = ctRegex!(r"^([^#]*?)\s+->\s+(\.?)(.*)"); // 160 MB RAM.
alias slZip = curry!(zip, StoppingPolicy.requireSameLength);
foreach (test, const rule; slZip(tests, rules)) {
const origTest = test.dup;
string[][] capt;
foreach (const line; rule) {
auto m = line.match(re);
if (!m.empty) {
//capt.put(m.captures.dropOne);
capt ~= m.captures.dropOne.array;
}
}
REDO:
const copy = test;
foreach (const c; capt) {
test = test.replace(c[0], c[2]);
if (c[1] == ".")
break;
if (test != copy)
goto REDO;
}
writefln("%s\n%s\n", origTest, test);
}
}</lang>
- Output:
I bought a B of As from T S. I bought a bag of apples from my brother. I bought a B of As from T S. I bought a bag of apples from T shop. I bought a B of As W my Bgage from T S. I bought a bag of apples with my money from T shop. _1111*11111_ 11111111111111111111 000000A000000 00011H1111000
Déjà Vu
This implementation expect the initial text on the command line and the ruleset on STDIN. <lang dejavu>(remove-comments) text: ] for line in text: if and line not starts-with line "#": line [
(markov-parse) text: ] for line in text: local :index find line " -> " local :pat slice line 0 index local :rep slice line + index 4 len line local :term starts-with rep "." if term: set :rep slice rep 1 len rep & pat & term rep [
markov-parse: (markov-parse) (remove-comments) split !decode!utf-8 !read!stdin "\n"
(markov-tick) rules start: for rule in copy rules: local :pat &< rule local :rep &> dup &> rule local :term &< local :index find start pat if < -1 index: ) slice start + index len pat len start rep slice start 0 index concat( return term true start
markov rules: true while: not (markov-tick) rules
!. markov markov-parse get-from !args 1</lang>
EchoLisp
<lang scheme>
- rule
- = (pattern replacement [#t terminal])
(define-syntax-rule (pattern rule) (first rule)) (define-syntax-rule (repl sule) (second rule)) (define-syntax-rule (term? rule) (!empty? (cddr rule)))
- (alpha .beta )--> (alpha beta #t)
(define (term-rule rule)
(if (string=? (string-first (repl rule)) ".")
(list (pattern rule) (string-rest (repl rule)) #t)
rule ))
- returns list of rules
(define (parse-rules lines)
(map term-rule
(for/list [(line (string-split lines "\n"))]
#:continue (string=? (string-first line) "#")
(map string-trim
(string-split (string-replace line "/\\t/g" " ") " -> ")))))
- markov machine
(define (markov i-string rules)
(while
(for/fold (run #f) ((rule rules))
#:when (string-index (pattern rule) i-string)
(set! i-string (string-replace i-string (pattern rule) (repl rule)))
;;(writeln rule i-string) ;; uncomment for trace
#:break (term? rule) => #f
#:break #t => #t ))
i-string)
(define (task i-string RS)
(markov i-string (parse-rules RS)))
</lang>
- Output:
(define RS1 #<<
# This rules file is extracted from Wikipedia:
# http://en.wikipedia.org/wiki/Markov_Algorithm
A -> apple
B -> bag
C -> chinchard
S -> shop
T -> the
the shop -> my brother
a never used -> .terminating rule
>>#)
;; [ Other rules sets here ...]
(define i-string-1 "I bought a B of As and Cs from T S.")
(define i-string-2 "I bought a B of As from T S.")
(define i-string-3 "I bought a B of As W my Bgage from T S.")
(define i-string-4 "_1111*11111_")
(define i-string-5 "000000A000000")
(task i-string-1 RS1)
→ "I bought a bag of apples and chinchards from my brother."
(task i-string-2 RS2)
→ "I bought a bag of apples from T shop."
(task i-string-3 RS3)
→ "I bought a bag of apples with my money from T shop."
(task i-string-4 RS4)
→ "11111111111111111111"
(task i-string-5 RS5)
→ "00011H1111000"
Go
<lang go>package main
import (
"fmt" "strings"
)
type testCase struct {
ruleSet, sample, output string
}
var testSet []testCase // initialized in separate source file
func main() {
fmt.Println("validating", len(testSet), "test cases")
var failures bool
for i, tc := range testSet {
if r := ma(tc.ruleSet, tc.sample); r != tc.output {
fmt.Println("test", i+1, "fail")
failures = true
}
}
if !failures {
fmt.Println("no failures")
}
}
type rule struct {
pat string rep string term bool
}
func ma(rs, s string) string {
// compile rules per task description
var rules []rule
for _, line := range strings.Split(rs, "\n") {
if line == "" || line[0] == '#' {
continue
}
a := strings.Index(line, "->")
if a == -1 {
fmt.Println("invalid rule:", line)
return ""
}
pat := line[:a]
for {
if pat == "" {
b := strings.Index(line[a+2:], "->")
if b == -1 {
fmt.Println("invalid rule:", line)
return ""
}
a += 2 + b
pat = line[:a]
continue
}
last := pat[len(pat)-1]
if last != ' ' && last != '\t' {
break
}
pat = pat[:len(pat)-1]
}
rep := line[a+2:]
for rep > "" && (rep[0] == ' ' || rep[0] == '\t') {
rep = rep[1:]
}
var term bool
if rep > "" && rep[0] == '.' {
term = true
rep = rep[1:]
}
rules = append(rules, rule{pat, rep, term})
}
// execute algorithm per WP
for r := 0; r < len(rules); {
pat := rules[r].pat
if f := strings.Index(s, pat); f == -1 {
r++
} else {
s = s[:f] + rules[r].rep + s[f+len(pat):]
if rules[r].term {
break
}
r = 0
}
}
return s
}</lang> The rule set source file contains all the strings as literals, packaged into a data structure. It starts like this, <lang go> package main
func init() {
testSet = []testCase{
{
`# This rules file is extracted from Wikipedia:
A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule`,
"I bought a B of As from T S.",
"I bought a bag of apples from my brother."},
{
`# Slightly modified from the rules on Wikipedia A -> apple B -> bag ... </lang> Compile both files, link, and run. Output:
validating 5 test cases no failures
Groovy
<lang groovy>def markovInterpreterFor = { rules ->
def ruleMap = [:]
rules.eachLine { line ->
(line =~ /\s*(.+)\s->\s([.]?)(.+)\s*/).each { text, key, terminating, value ->
if (key.startsWith('#')) { return }
ruleMap[key] = [text: value, terminating: terminating]
}
}
[interpret: { text ->
def originalText =
while (originalText != text) {
originalText = text
for (Map.Entry e : ruleMap.entrySet()) {
if (text.indexOf(e.key) >= 0) {
text = text.replace(e.key, e.value.text)
if (e.value.terminating) {
return text
}
break
}
}
}
text
}]
}</lang> The test code is below (with the markov rulesets 2..5 elided): <lang groovy>def verify = { ruleset ->
[withInput: { text ->
[hasOutput: { expected ->
def result = ruleset.interpret(text)
println "Input: '$text' has output: '$result'"
assert expected == result
}]
}]
}
def ruleset1 = markovInterpreterFor("""
- This rules file is extracted from Wikipedia:
- http://en.wikipedia.org/wiki/Markov_Algorithm
A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule""") println ruleset1.interpret('I bought a B of As from T S.') verify ruleset1 withInput 'I bought a bag of apples from T shop.' hasOutput 'I bought a bag of apples from my brother.'
def ruleset2 = markovInterpreterFor("""...""") verify ruleset2 withInput 'I bought a B of As from T S.' hasOutput 'I bought a bag of apples from T shop.'
def ruleset3 = markovInterpreterFor("""...""") verify ruleset3 withInput 'I bought a B of As W my Bgage from T S.' hasOutput 'I bought a bag of apples with my money from T shop.'
def ruleset4 = markovInterpreterFor("""...""") verify ruleset4 withInput '_1111*11111_' hasOutput '11111111111111111111'
def ruleset5 = markovInterpreterFor("""...""") verify ruleset5 withInput '000000A000000' hasOutput '00011H1111000'</lang>
- Output:
I bought a bag of apples from my brother. Input: 'I bought a bag of apples from T shop.' has output: 'I bought a bag of apples from my brother.' Input: 'I bought a B of As from T S.' has output: 'I bought a bag of apples from T shop.' Input: 'I bought a B of As W my Bgage from T S.' has output: 'I bought a bag of apples with my money from T shop.' Input: '_1111*11111_' has output: '11111111111111111111' Input: '000000A000000' has output: '00011H1111000'
Haskell
This program expects a source file as an argument and uses the standard input and output devices for the algorithm's I/O.
<lang haskell>import Data.List (isPrefixOf) import Data.Maybe (catMaybes) import Control.Monad import Text.ParserCombinators.Parsec import System.IO import System.Environment (getArgs)
main = do
args <- getArgs
unless (length args == 1) $
fail "Please provide exactly one source file as an argument."
let sourcePath = head args
source <- readFile sourcePath
input <- getContents
case parse markovParser sourcePath source of
Right rules -> putStr $ runMarkov rules input
Left err -> hPutStrLn stderr $ "Parse error at " ++ show err
data Rule = Rule
{from :: String, terminating :: Bool, to :: String}
markovParser :: Parser [Rule] markovParser = liftM catMaybes $
(comment <|> rule) `sepEndBy` many1 newline
where comment = char '#' >> skipMany nonnl >> return Nothing
rule = liftM Just $ liftM3 Rule
(manyTill (nonnl <?> "pattern character") $ try arrow)
(succeeds $ char '.')
(many nonnl)
arrow = ws >> string "->" >> ws <?> "whitespace-delimited arrow"
nonnl = noneOf "\n"
ws = many1 $ oneOf " \t"
succeeds p = option False $ p >> return True
runMarkov :: [Rule] -> String -> String runMarkov rules s = f rules s
where f [] s = s
f (Rule from terminating to : rs) s = g "" s
where g _ "" = f rs s
g before ahead@(a : as) = if from `isPrefixOf` ahead
then let new = reverse before ++ to ++ drop (length from) ahead
in if terminating then new else f rules new
else g (a : before) as</lang>
Icon and Unicon
<lang unicon>procedure main(A)
rules := loadRules(open(A[1],"r")) every write(line := !&input, " -> ",apply(rules, line))
end
record rule(pat, term, rep)
procedure loadRules(f)
rules := []
every !f ? if not ="#" then put(rules,
rule(1(trim(tab(find("->"))),move(2),tab(many(' \t'))),
(="."|&null), trim(tab(0))))
return rules
end
procedure apply(rules, line)
s := line
repeat {
s ?:= tab(find((r := !rules).pat)) || r.rep || (move(*r.pat),tab(0))
if (s == line) | \r.term then return s else line := s
}
end</lang>
Sample runs using above rule sets and test strings:
->ma mars.1 I bought a B of As from T S. I bought a B of As from T S. -> I bought a bag of apples from my brother. ->ma mars.2 I bought a B of As from T S. I bought a B of As from T S. -> I bought a bag of apples from T shop. ->ma mars.3 I bought a B of As W my Bgage from T S. I bought a B of As W my Bgage from T S. -> I bought a bag of apples with my money from T shop. ->ma mars.4 _1111*11111_ _1111*11111_ -> 11111111111111111111 ->ma mars.5 000000A000000 000000A000000 -> 00011H1111000
J
Solution:<lang j>require'strings regex'
markovLexer =: verb define
rules =. LF cut TAB&=`(,:&' ')}y
rules =. a: -.~ (dltb@:{.~ i:&'#')&.> rules
rules =. 0 _1 {"1 '\s+->\s+' (rxmatch rxcut ])S:0 rules
(,. ] (}.&.>~ ,. ]) ('.'={.)&.>)/ |: rules
)
replace =: dyad define
'index patternLength replacement'=. x 'head tail' =. index split y head, replacement, patternLength }. tail
)
matches =: E. i. 1:
markov =: dyad define
ruleIdx =. 0 [ rules =. markovLexer x
while. ruleIdx < #rules do.
'pattern replacement terminating' =. ruleIdx { rules
ruleIdx =. 1 + ruleIdx
if. (#y) > index =. pattern matches y do.
y =. (index ; (#pattern) ; replacement) replace y
ruleIdx =. _ * terminating
end.
end.
y
)</lang>
Example:<lang j> m1 =. noun define # This rules file is extracted from Wikipedia: # http://en.wikipedia.org/wiki/Markov_Algorithm A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule )
m1 markov 'I bought a B of As from T S.'
I bought a bag of apples from my brother. </lang> Discussion: The J implementation correctly processes all the rulesets. More details are available on the the talk page.
Java
<lang java>import java.io.IOException; import java.nio.charset.StandardCharsets; import java.nio.file.Files; import java.nio.file.Paths; import java.util.ArrayList; import java.util.List; import java.util.regex.Matcher; import java.util.regex.Pattern;
public class Markov {
public static void main(String[] args) throws IOException {
List<String[]> rules = readRules("markov_rules.txt");
List<String> tests = readTests("markov_tests.txt");
Pattern pattern = Pattern.compile("^([^#]*?)\\s+->\\s+(\\.?)(.*)");
for (int i = 0; i < tests.size(); i++) {
String origTest = tests.get(i);
List<String[]> captures = new ArrayList<>();
for (String rule : rules.get(i)) {
Matcher m = pattern.matcher(rule);
if (m.find()) {
String[] groups = new String[m.groupCount()];
for (int j = 0; j < groups.length; j++)
groups[j] = m.group(j + 1);
captures.add(groups);
}
}
String test = origTest;
String copy = test;
for (int j = 0; j < captures.size(); j++) {
String[] c = captures.get(j);
test = test.replace(c[0], c[2]);
if (c[1].equals("."))
break;
if (!test.equals(copy)) {
j = -1; // redo loop
copy = test;
}
}
System.out.printf("%s\n%s\n\n", origTest, test);
}
}
private static List<String> readTests(String path)
throws IOException {
return Files.readAllLines(Paths.get(path), StandardCharsets.UTF_8);
}
private static List<String[]> readRules(String path)
throws IOException {
String ls = System.lineSeparator();
String lines = new String(Files.readAllBytes(Paths.get(path)), "UTF-8");
List<String[]> rules = new ArrayList<>();
for (String line : lines.split(ls + ls))
rules.add(line.split(ls));
return rules;
}
}</lang>
Output:
I bought a B of As from T S. I bought a bag of apples from my brother. I bought a B of As from T S. I bought a bag of apples from T shop. I bought a B of As W my Bgage from T S. I bought a bag of apples with my money from T shop. _1111*11111_ 11111111111111111111 000000A000000 00011H1111000
Lua
<lang lua>-- utility method to escape punctuation function normalize(str) local result = str:gsub("(%p)", "%%%1") -- print(result) return result end
-- utility method to split string into lines function get_lines(str) local t = {} for line in str:gmatch("([^\n\r]*)[\n\r]*") do table.insert(t, line) end return t end
local markov = {} local MARKOV_RULE_PATTERN = "(.+)%s%-%>%s(%.?)(.*)"
function markov.rule(pattern,replacement,terminating) return { pattern = pattern, replacement = replacement, terminating = (terminating == ".") }, normalize(pattern) end
function markov.make_rules(sample) local lines = get_lines(sample) local rules = {} local finders = {} for i,line in ipairs(lines) do if not line:find("^#") then s,e,pat,term,rep = line:find(MARKOV_RULE_PATTERN) if s then r, p = markov.rule(pat,rep,term) rules[p] = r table.insert(finders, p) end end end return { rules = rules, finders = finders } end
function markov.execute(state, sample_input)
local rules, finders = state.rules, state.finders local found = false -- did we find any rule? local terminate = false
repeat found = false
for i,v in ipairs(finders) do local found_now = false -- did we find this rule? if sample_input:find(v) then found = true found_now = true end sample_input = sample_input:gsub(v, rules[v].replacement, 1) -- handle terminating rules if found_now then if rules[v].terminating then terminate = true end break end end
until not found or terminate
return sample_input end
local grammar1 = [[
- This rules file is extracted from Wikipedia:
- http://en.wikipedia.org/wiki/Markov_Algorithm
A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule ]]
local grammar2 = [[
- Slightly modified from the rules on Wikipedia
A -> apple B -> bag S -> .shop T -> the the shop -> my brother a never used -> .terminating rule ]]
local grammar3 = [[
- BNF Syntax testing rules
A -> apple WWWW -> with Bgage -> ->.* B -> bag ->.* -> money W -> WW S -> .shop T -> the the shop -> my brother a never used -> .terminating rule ]]
local grammar4 = [[
- Unary Multiplication Engine, for testing Markov Algorithm implementations
- By Donal Fellows.
- Unary addition engine
_+1 -> _1+ 1+1 -> 11+
- Pass for converting from the splitting of multiplication into ordinary
- addition
1! -> !1 ,! -> !+ _! -> _
- Unary multiplication by duplicating left side, right side times
1*1 -> x,@y 1x -> xX X, -> 1,1 X1 -> 1X _x -> _X ,x -> ,X y1 -> 1y y_ -> _
- Next phase of applying
1@1 -> x,@y 1@_ -> @_ ,@_ -> !_ ++ -> +
- Termination cleanup for addition
_1 -> 1 1+_ -> 1 _+_ -> ]]
local grammar5 = [[
- Turing machine: three-state busy beaver
- state A, symbol 0 => write 1, move right, new state B
A0 -> 1B
- state A, symbol 1 => write 1, move left, new state C
0A1 -> C01 1A1 -> C11
- state B, symbol 0 => write 1, move left, new state A
0B0 -> A01 1B0 -> A11
- state B, symbol 1 => write 1, move right, new state B
B1 -> 1B
- state C, symbol 0 => write 1, move left, new state B
0C0 -> B01 1C0 -> B11
- state C, symbol 1 => write 1, move left, halt
0C1 -> H01 1C1 -> H11 ]]
local text1 = "I bought a B of As from T S." local text2 = "I bought a B of As W my Bgage from T S." local text3 = '_1111*11111_' local text4 = '000000A000000'
function do_markov(rules, input, output) local m = markov.make_rules(rules) input = markov.execute(m, input) assert(input == output) print(input) end
do_markov(grammar1, text1, 'I bought a bag of apples from my brother.') do_markov(grammar2, text1, 'I bought a bag of apples from T shop.') -- stretch goals do_markov(grammar3, text2, 'I bought a bag of apples with my money from T shop.') do_markov(grammar4, text3, '11111111111111111111') do_markov(grammar5, text4, '00011H1111000')</lang>
Mathematica / Wolfram Language
<lang mathematica>markov[ruleset_, text_] :=
Module[{terminating = False, output = text,
rules = StringCases[
ruleset, {StartOfLine ~~ pattern : Except["\n"] .. ~~
" " | "\t" .. ~~ "->" ~~ " " | "\t" .. ~~ dot : "" | "." ~~
replacement : Except["\n"] .. ~~ EndOfLine :> {pattern,
replacement, dot == "."}}]},
While[! terminating, terminating = True;
Do[If[! StringFreeQ[output, rule1],
output = StringReplace[output, rule1 -> rule2];
If[! rule3, terminating = False]; Break[]], {rule, rules}]];
output];</lang>
Example: <lang mathematica>markov["# Turing machine: three-state busy beaver
# # state A, symbol 0 => write 1, move right, new state B A0 -> 1B # state A, symbol 1 => write 1, move left, new state C 0A1 -> C01 1A1 -> C11 # state B, symbol 0 => write 1, move left, new state A 0B0 -> A01 1B0 -> A11 # state B, symbol 1 => write 1, move right, new state B B1 -> 1B # state C, symbol 0 => write 1, move left, new state B 0C0 -> B01 1C0 -> B11 # state C, symbol 1 => write 1, move left, halt 0C1 -> H01 1C1 -> H11", "000000A000000"]</lang>
Output:
"00011H1111000"
МК-61/52
<lang> 9 П4 КИП4 [x] П7 Вx {x} П8 ИП8 ИПE * П8 {x} x=0 08 П5 ИП9 П1 lg [x] 10^x П3 ИП1 П2 Сx П6 ИП2 ИП7 - x=0 70 ИП9 ^ lg [x] 1 + ИП5 - 10^x / [x] ИП6 ИП8 x#0 50 lg [x] 1 + + 10^x * ИП9 ИП6 10^x П7 / {x} ИП7 * + ИП8 ИП7 * + П9 С/П БП 00 x>=0 80 КИП6 ИП2 ИПE / [x] П2 x=0 26 КИП5 ИП1 ИП3 / {x} ИП3 * П1 ИП3 ИПE / [x] П3 x=0 22 ИП4 ИП0 - 9 - x=0 02 С/П</lang>
Under the rules of left 4 registers, under the word has 8 character cells, the alphabet of the digits from 1 to 8. Rules are placed in "123,456", where "123" is a fragment, and "456" is to be replaced, in the registers of the РA to РD. The number of rules is stored in Р0, the initial word is in Р9. Number triggered rule is the last digit registration Р4 (0 to 3), if no rule did not work, the indicator 0, otherwise the current word to be processed. In РE is stored 10.
OCaml
I'm not familiar with string processing, or parsing, so there are probably better ways to express this in OCaml. One might be with the mikmatch library which allows pattern-matching with regexps. Here I've only used the OCaml stdlib...
<lang OCaml>(* Useful for resource cleanup (such as filehandles) *) let try_finally x f g =
try let res = f x in g x; res with e -> g x; raise e
(* Substitute string 'b' for first occurance of regexp 'a' in 's';
* Raise Not_found if there was no occurance of 'a'. *)
let subst a b s =
ignore (Str.search_forward a s 0); (* to generate Not_found *) Str.replace_first a b s
let parse_rules cin =
let open Str in
let rule = regexp "\\(.+\\)[ \t]+->[ \t]+\\(.*\\)" in
let leader s c = String.length s > 0 && s.[0] = c in
let parse_b s = if leader s '.' then (string_after s 1,true) else (s,false) in
let rec parse_line rules =
try
let s = input_line cin in
if leader s '#' then parse_line rules
else if string_match rule s 0 then
let a = regexp_string (matched_group 1 s) in
let b,terminate = parse_b (matched_group 2 s) in
parse_line ((a,b,terminate)::rules)
else failwith ("parse error: "^s)
with End_of_file -> rules
in List.rev (parse_line [])
let rec run rules text =
let rec apply s = function
| [] -> s
| (a,b,term)::next ->
try
let s' = subst a b s in
if term then s' else run rules s'
with Not_found -> apply s next
in apply text rules
let _ =
if Array.length Sys.argv <> 2 then
print_endline "Expecting one argument: a filename where rules can be found."
else
let rules = try_finally (open_in Sys.argv.(1)) parse_rules close_in in
(* Translate lines read from stdin, until EOF *)
let rec translate () =
print_endline (run rules (input_line stdin));
translate ()
in try translate () with End_of_file -> ()</lang>
With the above compiled to an executable 'markov', and the five rule-sets in files, strings are accepted on stdin for translation:
<~/rosetta$> markov rules1 I bought a B of As from T S. I bought a bag of apples from my brother. <~/rosetta$> markov rules2 I bought a B of As from T S. I bought a bag of apples from T shop. <~/rosetta$> markov rules3 I bought a B of As W my Bgage from T S. I bought a bag of apples with my money from T shop. <~/rosetta$> markov rules4 _1111*11111_ 11111111111111111111 <~/rosetta$> markov rules5 000000A000000 00011H1111000
Perl
This program expects a source file as an argument and uses the standard input and output devices for the algorithm's I/O.
<lang perl>@ARGV == 1 or die "Please provide exactly one source file as an argument.\n"; open my $source, '<', $ARGV[0] or die "I couldn't open \"$ARGV[0]\" for reading. ($!.)\n"; my @rules; while (<$source>)
{/\A#/ and next;
my @a = /(.*?)\s+->\s+(\.?)(.*)/ or die "Syntax error: $_";
push @rules, \@a;}
close $source;
my $input = do {local $/; <STDIN>;};
OUTER:
{foreach (@rules)
{my ($from, $terminating, $to) = @$_;
$input =~ s/\Q$from\E/$to/
and ($terminating ? last OUTER : redo OUTER);}}
print $input;</lang>
Perl 6
Run this without arguments and it will scan the cwd for rules.* files and their corresponding test.*.
Run it with two filenames or one filename and some text to run a rulefile on the file contents or the given text.
Add --verbose to see the replacements step-by-step.
<lang Perl6>grammar Markov {
token TOP {
^ [^^ [<rule> | <comment>] $$ [\n|$]]* $
{ make $<rule>>>.ast }
}
token comment {
<before ^^> '#' \N*
{ make Nil }
}
token ws {
[' '|\t]*
}
rule rule {
<before ^^>$<pattern>=[\N+?] '->'
$<terminal>=[\.]?$<replacement>=[\N*]
{ make {:pattern($<pattern>.Str),
:replacement($<replacement>.Str),
:terminal($<terminal>.Str eq ".")} }
}
}
sub run(:$ruleset, :$start_value, :$verbose?) {
my $value = $start_value;
my @rules = Markov.parse($ruleset).ast.list;
loop {
my $beginning = $value;
for @rules {
my $prev = $value;
$value = $value.subst(.<pattern>, .<replacement>);
say $value if $verbose && $value ne $prev;
return $value if .<terminal>;
last if $value ne $prev;
}
last if $value eq $beginning;
}
return $value;
}
multi sub MAIN(Bool :$verbose?) {
my @rulefiles = dir.grep(/rules.+/).sort;
for @rulefiles -> $rulefile {
my $testfile = $rulefile.subst("rules", "test");
my $start_value = (try slurp($testfile).trim-trailing)
// prompt("please give a start value: ");
my $ruleset = slurp($rulefile);
say $start_value.perl();
say run(:$ruleset, :$start_value, :$verbose).perl;
say ;
}
}
multi sub MAIN(Str $rulefile where *.IO.f, Str $input where *.IO.f, Bool :$verbose?) {
my $ruleset = slurp($rulefile); my $start_value = slurp($input).trim-trailing; say "starting with $start_value.perl()"; say run(:$ruleset, :$start_value, :$verbose).perl;
}
multi sub MAIN(Str $rulefile where *.IO.f, *@pieces, Bool :$verbose?) {
my $ruleset = slurp($rulefile);
my $start_value = @pieces.join(" ");
say "starting with $start_value.perl()";
say run(:$ruleset, :$start_value, :$verbose).perl;
}</lang>
PicoLisp
<lang PicoLisp>(de markov (File Text)
(use (@A @Z R)
(let Rules
(make
(in File
(while (skip "#")
(when (match '(@A " " "-" ">" " " @Z) (replace (line) "@" "#"))
(link (cons (clip @A) (clip @Z))) ) ) ) )
(setq Text (chop Text))
(pack
(loop
(NIL
(find
'((R) (match (append '(@A) (car R) '(@Z)) Text))
Rules )
Text )
(T (= "." (cadr (setq R @)))
(append @A (cddr R) @Z) )
(setq Text (append @A (cdr R) @Z)) ) ) ) ) )</lang>
Output:
: (markov "r1" "I bought a B of As from T S.") -> "I bought a bag of apples from my brother." : (markov "r2" "I bought a B of As from T S.") -> "I bought a bag of apples from T shop." : (markov "r3" "I bought a B of As W my Bgage from T S.") -> "I bought a bag of apples with my money from T shop." : (markov "r4" "_1111*11111_") -> "11111111111111111111" : (markov "r5" "000000A000000") -> "00011H1111000"
Prolog
Works with SWI-Prolog and module(library(lambda)).
Module lambda can be found there : http://www.complang.tuwien.ac.at/ulrich/Prolog-inedit/lambda.pl
<lang prolog>:- module('markov.pl', [markov/3, apply_markov/3]).
- - use_module(library(lambda)).
apply_markov(Rules, Sentence, Replacement) :- maplist(\X^Y^(atom_chars(X, Ch), phrase(markov(Y), Ch, [])), Rules, TmpRules), % comments produce empty rules exclude(=([]), TmpRules, LstRules),
atom_chars(Sentence, L), apply_rules(L, LstRules, R), atom_chars(Replacement, R).
apply_rules(In, Rules, Out ) :- apply_one_rule(In, Rules, Out1, Keep_On), ( Keep_On = false -> Out = Out1 ; apply_rules(Out1, Rules, Out)).
apply_one_rule(In, [Rule | Rules], Out, Keep_On) :-
extract(Rule, In, Out1, KeepOn),
( KeepOn = false
-> Out = Out1, Keep_On = KeepOn
; (KeepOn = stop
-> Out = Out1,
Keep_On = true
; apply_one_rule(Out1, Rules, Out, Keep_On))).
apply_one_rule(In, [], In, false) .
extract([Pattern, Replace], In, Out, Keep_On) :-
( Replace = [.|Rest]
-> R = Rest
; R = Replace),
( (append(Pattern, End, T), append(Deb, T, In))
-> extract([Pattern, Replace], End, NewEnd, _Keep_On),
append_3(Deb, R, NewEnd, Out),
Keep_On = stop
; Out = In,
( R = Replace
-> Keep_On = true
; Keep_On = false)).
append_3(A, B, C, D) :-
append(A, B, T),
append(T, C, D).
% creation of the rules markov(A) --> line(A).
line(A) --> text(A), newline.
newline --> ['\n'], newline.
newline --> [].
text([]) --> comment([]). text(A) --> rule(A).
comment([]) --> ['#'], anything.
anything --> [X], {X \= '\n'}, anything. anything --> ['\n']. anything --> [].
rule([A,B]) --> pattern(A), whitespaces, ['-', '>'], whitespaces, end_rule(B).
pattern([X | R]) --> [X], {X \= '\n'}, pattern(R). pattern([]) --> [].
whitespaces --> ['\t'], whitespace. whitespaces --> [' '], whitespace.
whitespace --> whitespaces. whitespace --> [].
end_rule([.| A]) --> [.], rest_of_rule(A). end_rule(A) --> rest_of_rule(A). end_rule([]) --> [].
rest_of_rule(A) --> replacement(A).
replacement([X | R]) --> [X], {X \= '\n'}, replacement(R). replacement([]) --> []. </lang> Code to test : <lang Prolog>:- use_module('markov.pl').
- - use_module(library(lambda)).
markov :- maplist(\X^(call(X), nl,nl), [markov_1, markov_2, markov_3, markov_4, markov_5]).
markov_1 :- A = ['# This rules file is extracted from Wikipedia:', '# http://en.wikipedia.org/wiki/Markov_Algorithm', 'A -> apple', 'B -> bag', 'S -> shop', 'T -> the', 'the shop -> my brother', 'a never used -> .terminating rule'], B = 'I bought a B of As from T S.', apply_markov(A, B, R), writeln(B), writeln(R).
markov_2 :-
A = ['# Slightly modified from the rules on Wikipedia',
'A -> apple',
'B -> bag',
'S -> .shop',
'T -> the',
'the shop -> my brother',
'a never used -> .terminating rule'],
B = 'I bought a B of As from T S.',
apply_markov(A, B, R), writeln(B), writeln(R).
markov_3 :-
A = ['# BNF Syntax testing rules',
'A -> apple',
'WWWW -> with',
'Bgage -> ->.*',
'B -> bag',
'->.* -> money',
'W -> WW',
'S -> .shop',
'T -> the',
'the shop -> my brother',
'a never used -> .terminating rule'],
B = 'I bought a B of As W my Bgage from T S.',
apply_markov(A, B, R), writeln(B), writeln(R).
markov_4 :-
A = ['### Unary Multiplication Engine, for testing Markov Algorithm implementations',
'### By Donal Fellows.',
'# Unary addition engine',
'_+1 -> _1+',
'1+1 -> 11+',
'# Pass for converting from the splitting of multiplication into ordinary',
'# addition',
'1! -> !1',
',! -> !+',
'_! -> _',
'# Unary multiplication by duplicating left side, right side times',
'1*1 -> x,@y',
'1x -> xX',
'X, -> 1,1',
'X1 -> 1X',
'_x -> _X',
',x -> ,X',
'y1 -> 1y',
'y_ -> _',
'# Next phase of applying',
'1@1 -> x,@y',
'1@_ -> @_',
',@_ -> !_',
'++ -> +',
'# Termination cleanup for addition',
'_1 -> 1',
'1+_ -> 1',
'_+_ -> '],
B = '_1111*11111_',
apply_markov(A, B, R), writeln(B), writeln(R).
markov_5 :- A = ['# Turing machine: three-state busy beaver', '#', '# state A, symbol 0 => write 1, move right, new state B', 'A0 -> 1B', '# state A, symbol 1 => write 1, move left, new state C', '0A1 -> C01', '1A1 -> C11', '# state B, symbol 0 => write 1, move left, new state A', '0B0 -> A01', '1B0 -> A11', '# state B, symbol 1 => write 1, move right, new state B', 'B1 -> 1B', '# state C, symbol 0 => write 1, move left, new state B', '0C0 -> B01', '1C0 -> B11', '# state C, symbol 1 => write 1, move left, halt', '0C1 -> H01', '1C1 -> H11'],
B = '000000A000000', apply_markov(A, B, R), writeln(B), writeln(R). </lang> Output :
?- markov. I bought a B of As from T S. I bought a bag of apples from my brother. I bought a B of As from T S. I bought a bag of apples from T shop. I bought a B of As W my Bgage from T S. I bought a bag of apples with my money from T shop. _1111*11111_ 11111111111111111111 000000A000000 00011H1111000 true .
PureBasic
The GUI used here allows a ruleset to be loaded from a text file or manually added one rule at a time. Symbol input can be tested anytime by selecting 'Interpret'. <lang PureBasic>Structure mRule
pattern.s replacement.s isTerminal.i
EndStructure
Procedure parseRule(text.s, List rules.mRule())
#tab = 9: #space = 32: #whiteSpace$ = Chr(#space) + Chr(#tab)
Protected tLen, cPtr, nChar.c, pEnd, pLast, pattern.s
cPtr = 1
If FindString(#whiteSpace$, Left(text, cPtr), 1): ProcedureReturn 0: EndIf ;parse error
If Left(text, cPtr) = "#": ProcedureReturn 2: EndIf ;comment skipped
tLen = Len(text)
Repeat
cPtr + 1
If cPtr > tLen: ProcedureReturn 0: EndIf ;parse error
nChar = Asc(Mid(text, cPtr, 1))
Select nChar
Case #space, #tab
Select pEnd
Case 0 To 2
pEnd = 1
pLast = cPtr - 1
Case 3
pattern = Left(text, pLast)
EndSelect
Case '-'
If pEnd = 1: pEnd = 2: EndIf
Case '>'
If pEnd = 2: pEnd = 3: EndIf
EndSelect
Until pattern <> ""
Repeat
cPtr + 1
Until Not FindString(#whiteSpace$, Mid(text, cPtr, 1), 1)
Protected isTerminal
If Mid(text, cPtr, 1) = "."
isTerminal = #True: cPtr + 1
EndIf
LastElement(rules()): AddElement(rules())
rules()\pattern = pattern
rules()\replacement = Right(text, tLen - cPtr + 1)
rules()\isTerminal = isTerminal
ProcedureReturn 1 ;processed rule
EndProcedure
Procedure.s interpretMarkov(text.s, List rules.mRule())
Repeat
madeReplacement = #False
ForEach rules()
If FindString(text, rules()\pattern, 1)
text = ReplaceString(text, rules()\pattern, rules()\replacement)
madeReplacement = #True: isFinished = rules()\isTerminal
Break
EndIf
Next
Until Not madeReplacement Or isFinished
ProcedureReturn text
EndProcedure
Procedure addRule(text.s, List rules.mRule())
Protected result = parseRule(text, rules()) Select result Case 0: AddGadgetItem(7, -1, "Invalid rule: " + #DQUOTE$ + text + #DQUOTE$) Case 1: AddGadgetItem(7, -1, "Added: " + #DQUOTE$ + text + #DQUOTE$) Case 2: AddGadgetItem(7, -1, "Comment: " + #DQUOTE$ + text + #DQUOTE$) EndSelect
EndProcedure
OpenWindow(0, 0, 0, 350, 300, "Markov Algorithm Interpreter", #PB_Window_SystemMenu) ButtonGadget(0, 45, 10, 75, 20, "Load Ruleset") ButtonGadget(1, 163, 10, 65, 20, "Add Rule") ButtonGadget(2, 280, 10, 65, 20, "Interpret") TextGadget(3, 5, 40, 30, 20, "Input:") StringGadget(4, 45, 40, 300, 20,"") TextGadget(5, 5, 100, 35, 20, "Output:") ButtonGadget(6, 160, 70, 70, 20, "Clear Output") EditorGadget(7, 45, 100, 300, 195, #PB_Editor_ReadOnly)
NewList rules.mRule() Define event, isDone, text.s, result, file.s Repeat
event = WaitWindowEvent()
Select event
Case #PB_Event_Gadget
Select EventGadget()
Case 0
Define file.s, rule.s
file = OpenFileRequester("Select rule set", "*.txt", "Text (*.txt)|*.txt", 0)
If file
ClearList(rules())
ReadFile(0, file)
While Not(Eof(0))
addRule(ReadString(0), rules())
Wend
AddGadgetItem(7, -1, "Loaded " + Str(ListSize(rules())) + " rules."): AddGadgetItem(7, -1, "")
EndIf
Case 1
addRule(GetGadgetText(4), rules())
Case 2
text = GetGadgetText(4): AddGadgetItem(7, -1, "Interpret: " + #DQUOTE$ + text + #DQUOTE$)
AddGadgetItem(7, -1, "Result: " + #DQUOTE$ + interpretMarkov(text, rules()) + #DQUOTE$): AddGadgetItem(7, -1, "")
Case 6
ClearGadgetItems(7)
EndSelect
Case #PB_Event_CloseWindow
isDone = #True
EndSelect
Until isDone </lang> Sample output from loading Ruleset 1 and interpreting a symbol:
Comment: "# This rules file is extracted from Wikipedia:" Comment: "# http://en.wikipedia.org/wiki/Markov_Algorithm" Added: "A -> apple" Added: "B -> bag" Added: "S -> shop" Added: "T -> the" Added: "the shop -> my brother" Added: "a never used -> .terminating rule" Loaded 6 rules. Interpret: "I bought a B of As from T S." Result: "I bought a bag of apples from my brother."
Python
The example uses a regexp to parse the syntax of the grammar. This regexp is multi-line and verbose, and uses named groups to aid in understanding the regexp and to allow more meaningful group names to be used when extracting the replacement data from the grammars in function extractreplacements.
The example gains flexibility by not being tied to specific files. The functions may be imported into other programs which then can provide textual input from their sources without the need to pass 'file handles' around. <lang python>import re
def extractreplacements(grammar):
return [ (matchobj.group('pat'), matchobj.group('repl'), bool(matchobj.group('term')))
for matchobj in re.finditer(syntaxre, grammar)
if matchobj.group('rule')]
def replace(text, replacements):
while True:
for pat, repl, term in replacements:
if pat in text:
text = text.replace(pat, repl, 1)
if term:
return text
break
else:
return text
syntaxre = r"""(?mx) ^(?:
(?: (?P<comment> \# .* ) ) | (?: (?P<blank> \s* ) (?: \n | $ ) ) | (?: (?P<rule> (?P<pat> .+? ) \s+ -> \s+ (?P<term> \.)? (?P<repl> .+) ) )
)$ """
grammar1 = """\
- This rules file is extracted from Wikipedia:
- http://en.wikipedia.org/wiki/Markov_Algorithm
A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule """
grammar2 = \
- Slightly modified from the rules on Wikipedia
A -> apple B -> bag S -> .shop T -> the the shop -> my brother a never used -> .terminating rule
grammar3 = \
- BNF Syntax testing rules
A -> apple WWWW -> with Bgage -> ->.* B -> bag ->.* -> money W -> WW S -> .shop T -> the the shop -> my brother a never used -> .terminating rule
grammar4 = \
- Unary Multiplication Engine, for testing Markov Algorithm implementations
- By Donal Fellows.
- Unary addition engine
_+1 -> _1+ 1+1 -> 11+
- Pass for converting from the splitting of multiplication into ordinary
- addition
1! -> !1 ,! -> !+ _! -> _
- Unary multiplication by duplicating left side, right side times
1*1 -> x,@y 1x -> xX X, -> 1,1 X1 -> 1X _x -> _X ,x -> ,X y1 -> 1y y_ -> _
- Next phase of applying
1@1 -> x,@y 1@_ -> @_ ,@_ -> !_ ++ -> +
- Termination cleanup for addition
_1 -> 1 1+_ -> 1 _+_ ->
grammar5 = \
- Turing machine: three-state busy beaver
- state A, symbol 0 => write 1, move right, new state B
A0 -> 1B
- state A, symbol 1 => write 1, move left, new state C
0A1 -> C01 1A1 -> C11
- state B, symbol 0 => write 1, move left, new state A
0B0 -> A01 1B0 -> A11
- state B, symbol 1 => write 1, move right, new state B
B1 -> 1B
- state C, symbol 0 => write 1, move left, new state B
0C0 -> B01 1C0 -> B11
- state C, symbol 1 => write 1, move left, halt
0C1 -> H01 1C1 -> H11
text1 = "I bought a B of As from T S."
text2 = "I bought a B of As W my Bgage from T S."
text3 = '_1111*11111_'
text4 = '000000A000000'
if __name__ == '__main__':
assert replace(text1, extractreplacements(grammar1)) \
== 'I bought a bag of apples from my brother.'
assert replace(text1, extractreplacements(grammar2)) \
== 'I bought a bag of apples from T shop.'
# Stretch goals
assert replace(text2, extractreplacements(grammar3)) \
== 'I bought a bag of apples with my money from T shop.'
assert replace(text3, extractreplacements(grammar4)) \
== '11111111111111111111'
assert replace(text4, extractreplacements(grammar5)) \
== '00011H1111000'</lang>
Racket
The Markov algorithm interpreter
The Markov-algorithm for a set of rules returns a function which maps from a string to string and can be used as a first-class object. Rules are represented by abstract data structures.
<lang racket>
- lang racket
(struct -> (A B)) (struct ->. (A B))
(define ((Markov-algorithm . rules) initial-string)
(let/cc stop
; rewriting rules
(define (rewrite rule str)
(match rule
[(-> a b) (cond [(replace a str b) => apply-rules]
[else str])]
[(->. a b) (cond [(replace a str b) => stop]
[else str])]))
; the cycle through rewriting rules
(define (apply-rules s) (foldl rewrite s rules))
; the result is a fixed point of rewriting procedure
(fixed-point apply-rules initial-string)))
- replaces the first substring A to B in a string s
(define (replace A s B)
(and (regexp-match? (regexp-quote A) s)
(regexp-replace (regexp-quote A) s B)))
- Finds the least fixed-point of a function
(define (fixed-point f x0)
(let loop ([x x0] [fx (f x0)]) (if (equal? x fx) fx (loop fx (f fx)))))
</lang>
Example of use:
<lang racket> > (define MA
(Markov-algorithm
(-> "A" "apple")
(-> "B" "bag")
(->. "S" "shop")
(-> "T" "the")
(-> "the shop" "my brother")
(->. "a never used" "terminating rule")))
> (MA "I bought a B of As from T S.") "I bought a bag of apples from T shop." </lang>
The source reader
To read from a file just replace with-input-from-string ==> with-input-from-file.
<lang racket>
- the reader
(define (read-rules source)
(with-input-from-string source
(λ () (for*/list ([line (in-lines)]
#:unless (should-be-skipped? line))
(match line
[(rx-split A "blank:->blank:[.]" B) (->. A B)]
[(rx-split A "blank:->blank:" B) (-> A B)])))))
- the new pattern for the match form
(define-match-expander rx-split
(syntax-rules ()
[(rx-split A rx B)
(app (λ (s) (regexp-split (pregexp rx) s)) (list A B))]))
- skip empty lines and comments
(define (should-be-skipped? line)
(or (regexp-match? #rx"^#.*" line)
(regexp-match? #px"^blank:*$" line)))
(define (read-Markov-algorithm source)
(apply Markov-algorithm (read-rules source)))
</lang>
Examples:
<lang racket> (define R3 (read-Markov-algorithm "
- BNF Syntax testing rules
A -> apple WWWW -> with Bgage -> ->.* B -> bag ->.* -> money W -> WW S -> .shop T -> the the shop -> my brother a never used -> .terminating rule"))
(define R4
(read-Markov-algorithm "
- Unary Multiplication Engine, for testing Markov Algorithm implementations
- By Donal Fellows.
- Unary addition engine
_+1 -> _1+ 1+1 -> 11+
- Pass for converting from the splitting of multiplication into ordinary
- addition
1! -> !1 ,! -> !+ _! -> _
- Unary multiplication by duplicating left side, right side times
1*1 -> x,@y 1x -> xX X, -> 1,1 X1 -> 1X _x -> _X ,x -> ,X y1 -> 1y y_ -> _
- Next phase of applying
1@1 -> x,@y 1@_ -> @_ ,@_ -> !_ ++ -> +
- Termination cleanup for addition
_1 -> 1 1+_ -> 1 _+_ -> "))
(define R5
(read-Markov-algorithm "
- Turing machine: three-state busy beaver
- state A, symbol 0 => write 1, move right, new state B
A0 -> 1B
- state A, symbol 1 => write 1, move left, new state C
0A1 -> C01 1A1 -> C11
- state B, symbol 0 => write 1, move left, new state A
0B0 -> A01 1B0 -> A11
- state B, symbol 1 => write 1, move right, new state B
B1 -> 1B
- state C, symbol 0 => write 1, move left, new state B
0C0 -> B01 1C0 -> B11
- state C, symbol 1 => write 1, move left, halt
0C1 -> H01 1C1 -> H11")) </lang>
<lang racket> > (R3 "I bought a B of As W my Bgage from T S.") "I bought a bag of apples with my money from T shop."
> (R4 "_1111*11111_") "11111111111111111111"
> (R5 "000000A000000") "00011H1111000" </lang>
REXX
Code was added to the REXX example to optionally list the contents of the ruleset and/or the Markov entries.
Also, blank lines in the ruleset were treated as comments.
<lang rexx>/*REXX program executes a Markov algorithm(s) against specified entries. */
parse arg low high . /*allows which ruleset to process. */
if low== | low==',' then low=1 /*Not specified? Then use the default.*/
if high== | high==',' then high=6 /* " " " " " " */
tellE=low<0; tellR=high<0 /*flags: used to display file contents.*/
call readEntry
do j=abs(low) to abs(high) /*process each of these rulesets. */
call readRules j /*read a particular ruleset. */
call execRules j /*execute " " " */
say 'result for ruleset' j"≡"!.j
end /*j*/
exit /*stick a fork in it, we're all done. */ /*────────────────────────────────────────────────────────────────────────────*/ execRules: parse arg q .; if tellE | tellR then say /*a blank line*/
do f=1
do k=1 while @.k\==; if left(@.k,1)=='#' | @.k= then iterate
parse var @.k a ' ->' b; a=strip(a); b=strip(b)
fullstop= left(b,1)=='.' /*is this a "fullstop" rule? */
if fullstop then b=substr(b,2) /*purify the B part of the rule. */
old=!.q /*remember the value before the change.*/
!.q=changestr(a, !.q, b) /*implement the ruleset change. */
if fullstop then if old\==!.q then return /*should we stop? */
if old\==!.q then iterate f /*Has Entry changed? Then start over.*/
end /*k*/
leave
end /*f*/
return /*────────────────────────────────────────────────────────────────────────────*/ readRules: parse arg ? .; rFID='MARKOV_R.'?; if tellR then say @.= /*placeholder for all the Markov rules.*/
do r=1 while lines(rFID)\==0 /*read the input file until End-Of-File*/
@.r=linein(rFID); if tellR then say 'ruleSet' ?"."left(r,4)'≡'@.r
end /*r*/ /*(above) read and maybe echo the rule.*/
return /*────────────────────────────────────────────────────────────────────────────*/ readEntry: eFID='MARKOV.ENT'; if tellE then say !.= /*placeholder for all the test entries.*/
do e=1 while lines(eFID)\==0 /*read the input file until End-Of-File*/
!.e=linein(eFID); if tellE then say 'test entry' e"≡"!.e
end /*e*/ /*(above) read and maybe echo the entry*/
return</lang>
Some older REXXes don't have a changestr BIF, so one is included here ──► CHANGESTR.REX.
output when using the default input and files:
result for ruleset 1≡I bought a bag of apples from my brother. result for ruleset 2≡I bought a bag of apples from T shop. result for ruleset 3≡I bought a bag of apples with my money from T shop. result for ruleset 4≡11111111111111111111 result for ruleset 5≡00011H1111000 result for ruleset 6≡|||||
Ruleset 6 is:
# Rewrite binary numbers to their unary value (| bars). # I.E.: 101 [base 2] will be converted to 5 bars. #────────────────────────────────────────────────────── |0 -> 0|| 1 -> 0| 0 ->
Ruby
<lang Ruby>def setup(ruleset)
ruleset.each_line.inject([]) do |rules, line|
if line =~ /^\s*#/
rules
elsif line =~ /^(.+)\s+->\s+(\.?)(.*)$/
rules << [$1, $3, $2 != ""]
else
raise "Syntax error: #{line}"
end
end
end
def morcov(ruleset, input_data)
rules = setup(ruleset)
while (matched = rules.find { |match, replace, term|
input_data[match] and input_data.sub!(match, replace)
}) and !matched[2]
end
input_data
end</lang>
Test: <lang Ruby>ruleset1 = <<EOS
- This rules file is extracted from Wikipedia:
- http://en.wikipedia.org/wiki/Markov_Algorithm
A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule EOS
puts morcov(ruleset1, "I bought a B of As from T S.")
ruleset2 = <<EOS
- Slightly modified from the rules on Wikipedia
A -> apple B -> bag S -> .shop T -> the the shop -> my brother a never used -> .terminating rule EOS
puts morcov(ruleset2, "I bought a B of As from T S.")
ruleset3 = <<EOS
- BNF Syntax testing rules
A -> apple WWWW -> with Bgage -> ->.* B -> bag ->.* -> money W -> WW S -> .shop T -> the the shop -> my brother a never used -> .terminating rule EOS
puts morcov(ruleset3, "I bought a B of As W my Bgage from T S.")
ruleset4 = <<EOS
- Unary Multiplication Engine, for testing Markov Algorithm implementations
- By Donal Fellows.
- Unary addition engine
_+1 -> _1+ 1+1 -> 11+
- Pass for converting from the splitting of multiplication into ordinary
- addition
1! -> !1 ,! -> !+ _! -> _
- Unary multiplication by duplicating left side, right side times
1*1 -> x,@y 1x -> xX X, -> 1,1 X1 -> 1X _x -> _X ,x -> ,X y1 -> 1y y_ -> _
- Next phase of applying
1@1 -> x,@y 1@_ -> @_ ,@_ -> !_ ++ -> +
- Termination cleanup for addition
_1 -> 1 1+_ -> 1 _+_ -> EOS
puts morcov(ruleset4, "_1111*11111_")
ruleset5 = <<EOS
- Turing machine: three-state busy beaver
- state A, symbol 0 => write 1, move right, new state B
A0 -> 1B
- state A, symbol 1 => write 1, move left, new state C
0A1 -> C01 1A1 -> C11
- state B, symbol 0 => write 1, move left, new state A
0B0 -> A01 1B0 -> A11
- state B, symbol 1 => write 1, move right, new state B
B1 -> 1B
- state C, symbol 0 => write 1, move left, new state B
0C0 -> B01 1C0 -> B11
- state C, symbol 1 => write 1, move left, halt
0C1 -> H01 1C1 -> H11 EOS
puts morcov(ruleset5, "000000A000000")</lang>
- Output:
I bought a bag of apples from my brother. I bought a bag of apples from T shop. I bought a bag of apples with my money from T shop. 11111111111111111111 00011H1111000
Scala
<lang scala>import scala.io.Source
object MarkovAlgorithm {
val RulePattern = """(.*?)\s+->\s+(\.?)(.*)""".r
val CommentPattern = """#.*|\s*""".r
def rule(line: String) = line match {
case CommentPattern() => None
case RulePattern(pattern, terminal, replacement) => Some(pattern, replacement, terminal == ".")
case _ => error("Syntax error on line "+line)
}
def main(args: Array[String]) {
if (args.size != 2 ) {
println("Syntax: MarkovAlgorithm inputFile inputPattern")
exit(1)
}
val rules = (Source fromPath args(0) getLines () map rule).toList.flatten
def algorithm(input: String): String = rules find (input contains _._1) match {
case Some((pattern, replacement, true)) => input replaceFirst ("\\Q"+pattern+"\\E", replacement)
case Some((pattern, replacement, false)) => algorithm(input replaceFirst ("\\Q"+pattern+"\\E", replacement))
case None => input
}
println(args(1)) println(algorithm(args(1))) }
}</lang>
Script-style, and more concise:
<lang scala>import scala.io.Source
if (argv.size != 2 ) error("Syntax: MarkovAlgorithm inputFile inputPattern")
val rulePattern = """(.*?)\s+->\s+(\.?)(.*)""".r val isComment = (_: String) matches "#.*|\\s*" val rules = Source fromPath args(0) getLines () filterNot isComment map (rulePattern unapplySeq _ get) toList;
def algorithm(input: String): String = rules find (input contains _.head) match {
case Some(Seq(pattern, ".", replacement)) => input replaceFirst ("\\Q"+pattern+"\\E", replacement)
case Some(Seq(pattern, "", replacement)) => algorithm(input replaceFirst ("\\Q"+pattern+"\\E", replacement))
case None => input
}
println(argv(1)) println(algorithm(argv(1)))</lang>
Sample outputs:
C:\>scala MarkovAlgorithm ruleset1.txt "I bought a B of As from T S." I bought a B of As from T S. I bought a bag of apples from my brother. C:\>scala MarkovAlgorithm ruleset2.txt "I bought a B of As from T S." I bought a B of As from T S. I bought a bag of apples from T shop. C:\>scala MarkovAlgorithm ruleset3.txt "I bought a B of As W my Bgage from T S." I bought a B of As W my Bgage from T S. I bought a bag of apples with my money from T shop. C:\>scala MarkovAlgorithm ruleset4.txt "_1111*11111_" _1111*11111_ 11111111111111111111
The script is called much in the same way, but with the ".scala" extension added.
Scheme
The following implementation uses several string-related procedures provided by SRFI-13 [1].
<lang scheme> (define split-into-lines
(lambda (str)
(let loop ((index 0)
(result '()))
(let ((next-index (string-index str #\newline index)))
(if next-index
(loop (+ next-index 1)
(cons (substring str index next-index) result))
(reverse (cons (substring str index) result)))))))
(define parse-rules
(lambda (str)
(let loop ((rules (split-into-lines str))
(result '()))
(if (null? rules)
(reverse result)
(let ((rule (car rules)))
(loop (cdr rules)
(if (or (string=? rule "")
(eq? (string-ref rule 0) #\#))
result
(cons
(let ((index (string-contains rule "->" 1)))
(list (string-trim-right (substring rule 0 index))
(string-trim (substring rule (+ index 2)))))
result))))))))
(define apply-rules
(lambda (str rules)
(let loop ((remaining rules)
(result str))
(if (null? remaining)
result
(let* ((rule (car remaining))
(pattern (car rule))
(replacement (cadr rule))
(start (string-contains result pattern)))
(if start
(if (eq? #\. (string-ref replacement 0))
(string-replace result replacement start
(+ start (string-length pattern)) 1)
(apply-rules
(string-replace result replacement start
(+ start (string-length pattern)))
rules))
(loop (cdr remaining) result)))))))
</lang>
SNOBOL4
Note that the run-time data is immediately after the "end" label. This works with CSNOBOL4, on a Unix (or Unix-like) platform. The Markov rules are actually compiled into the program after parsing, and are then directly executed (self-modifying code). <lang SNOBOL4>
- !/bin/sh
exec "snobol4" "-r" "$0" "$@"
define('repl(s1,s2,s3)c,t,findc') :(repl_end)
repl s2 len(1) . c = :f(freturn)
findc = break(c) . t len(1)
s2 = pos(0) s2
repl_1 s1 findc = :f(repl_2)
s1 s2 = :f(repl_3)
repl = repl t s3 :(repl_1)
repl_3 repl = repl t c :(repl_1) repl_2 repl = repl s1 :(return) repl_end
define('quote(s)q,qq') :(quote_end)
quote q = "'"; qq = '"'
quote = q repl(s, q, q ' ' qq q qq ' ' q) q :(return)
quote_end
whitespace = span(' ' char(9))
top r = 0 read s = input :f(end)
s pos(0) 'ENDRULE' rpos(0) :s(interp)
s pos(0) '#' :s(read)
pattern =; replacement =; term =
s arb . pattern whitespace '->' whitespace
+ ('.' | ) . term arb . replacement rpos(0) :f(syntax)
r = r + 1
f = ident(term, '.') ' :(done)'
f = ident(term) ' :f(rule' r + 1 ')s(rule1)'
c = 'rule' r ' s ' quote(pattern) ' = ' quote(replacement) f
code(c) :s(read)
output = 'rule: ' s ' generates code ' c ' in error' :(end)
syntax output = 'rule: ' s ' in error' :(read) interp code('rule' r + 1 ' :(done)') go s = input :f(end)
s pos(0) 'END' rpos(0) :s(top)f(rule1)
done output = s :(go) end
- This rules file is extracted from Wikipedia:
- http://en.wikipedia.org/wiki/Markov_Algorithm
A -> apple B -> bag S -> shop T -> the the shop -> my brother a never used -> .terminating rule ENDRULE I bought a B of As from T S. END
- Slightly modified from the rules on Wikipedia
A -> apple B -> bag S -> .shop T -> the the shop -> my brother a never used -> .terminating rule ENDRULE I bought a B of As from T S. END
- BNF Syntax testing rules
A -> apple WWWW -> with Bgage -> ->.* B -> bag ->.* -> money W -> WW S -> .shop T -> the the shop -> my brother a never used -> .terminating rule ENDRULE I bought a B of As W my Bgage from T S. END
- Unary Multiplication Engine, for testing Markov Algorithm implementations
- By Donal Fellows.
- Unary addition engine
_+1 -> _1+ 1+1 -> 11+
- Pass for converting from the splitting of multiplication into ordinary
- addition
1! -> !1 ,! -> !+ _! -> _
- Unary multiplication by duplicating left side, right side times
1*1 -> x,@y 1x -> xX X, -> 1,1 X1 -> 1X _x -> _X ,x -> ,X y1 -> 1y y_ -> _
- Next phase of applying
1@1 -> x,@y 1@_ -> @_ ,@_ -> !_ ++ -> +
- Termination cleanup for addition
_1 -> 1 1+_ -> 1 _+_ -> ENDRULE _1111*11111_ END
- Turing machine: three-state busy beaver
- state A, symbol 0 => write 1, move right, new state B
A0 -> 1B
- state A, symbol 1 => write 1, move left, new state C
0A1 -> C01 1A1 -> C11
- state B, symbol 0 => write 1, move left, new state A
0B0 -> A01 1B0 -> A11
- state B, symbol 1 => write 1, move right, new state B
B1 -> 1B
- state C, symbol 0 => write 1, move left, new state B
0C0 -> B01 1C0 -> B11
- state C, symbol 1 => write 1, move left, halt
0C1 -> H01 1C1 -> H11 ENDRULE 000000A000000 END </lang>
Swift
<lang swift>import Foundation
func setup(ruleset: String) -> [(String, String, Bool)] {
return ruleset.componentsSeparatedByCharactersInSet(NSCharacterSet.newlineCharacterSet())
.filter { $0.rangeOfString("^s*#", options: .RegularExpressionSearch) == nil }
.reduce([(String, String, Bool)]()) { rules, line in
let regex = try! NSRegularExpression(pattern: "^(.+)\\s+->\\s+(\\.?)(.*)$", options: .CaseInsensitive)
guard let match = regex.firstMatchInString(line, options: .Anchored, range: NSMakeRange(0, line.characters.count)) else { return rules }
return rules + [(
(line as NSString).substringWithRange(match.rangeAtIndex(1)),
(line as NSString).substringWithRange(match.rangeAtIndex(3)),
(line as NSString).substringWithRange(match.rangeAtIndex(2)) != ""
)]
}
}
func markov(ruleset: String, var input: String) -> String {
let rules = setup(ruleset)
var terminate = false
while !terminate {
guard let i = rules.indexOf ({
if let range = input.rangeOfString($0.0) {
input.replaceRange(range, with: $0.1)
return true
}
return false
}) else { break }
terminate = rules[i].2
}
return input
}
let tests: [(ruleset: String, input: String)] = [
("# This rules file is extracted from Wikipedia:\n# http://en.wikipedia.org/wiki/Markov_Algorithm\nA -> apple\nB -> bag\nS -> shop\nT -> the\nthe shop -> my brother\na never used -> .terminating rule", "I bought a B of As from T S."),
("# Slightly modified from the rules on Wikipedia\nA -> apple\nB -> bag\nS -> .shop\nT -> the\nthe shop -> my brother\na never used -> .terminating rule", "I bought a B of As from T S."),
("# BNF Syntax testing rules\nA -> apple\nWWWW -> with\nBgage -> ->.*\nB -> bag\n->.* -> money\nW -> WW\nS -> .shop\nT -> the\nthe shop -> my brother\na never used -> .terminating rule", "I bought a B of As W my Bgage from T S."),
("### Unary Multiplication Engine, for testing Markov Algorithm implementations\n### By Donal Fellows.\n# Unary addition engine\n_+1 -> _1+\n1+1 -> 11+\n# Pass for converting from the splitting of multiplication into ordinary\n# addition\n1! -> !1\n,! -> !+\n_! -> _\n# Unary multiplication by duplicating left side, right side times\n1*1 -> x,@y\n1x -> xX\nX, -> 1,1\nX1 -> 1X\n_x -> _X\n,x -> ,X\ny1 -> 1y\ny_ -> _\n# Next phase of applying\n1@1 -> x,@y\n1@_ -> @_\n,@_ -> !_\n++ -> +\n# Termination cleanup for addition\n_1 -> 1\n1+_ -> 1\n_+_ ->", "_1111*11111_"),
("# Turing machine: three-state busy beaver\n#\n# state A, symbol 0 => write 1, move right, new state B\nA0 -> 1B\n# state A, symbol 1 => write 1, move left, new state C\n0A1 -> C01\n1A1 -> C11\n# state B, symbol 0 => write 1, move left, new state A\n0B0 -> A01\n1B0 -> A11\n# state B, symbol 1 => write 1, move right, new state B\nB1 -> 1B\n# state C, symbol 0 => write 1, move left, new state B\n0C0 -> B01\n1C0 -> B11\n# state C, symbol 1 => write 1, move left, halt\n0C1 -> H01\n1C1 -> H11", "000000A000000")
]
for (index, test) in tests.enumerate() {
print("\(index + 1):", markov(test.ruleset, input: test.input))
}
</lang>
- Output:
1: I bought a bag of apples from my brother. 2: I bought a bag of apples from T shop. 3: I bought a bag of apples with my money from T shop. 4: 11111111111111111111 5: 00011H1111000
Tcl
<lang tcl>package require Tcl 8.5 if {$argc < 3} {error "usage: $argv0 ruleFile inputFile outputFile"} lassign $argv ruleFile inputFile outputFile
- Read the file of rules
set rules {} set f [open $ruleFile] foreach line [split [read $f] \n[close $f]] {
if {[string match "#*" $line] || $line eq ""} continue
if {[regexp {^(.+)\s+->\s+(\.?)(.*)$} $line -> from final to]} {
lappend rules $from $to [string compare "." $final] [string length $from]
} else {
error "Syntax error: \"$line\""
}
}
- Apply the rules
set f [open $inputFile] set out [open $outputFile w] foreach line [split [read $f] \n[close $f]] {
set any 1
while {$any} {
set any 0 foreach {from to more fl} $rules { # If we match the 'from' pattern... if {[set idx [string first $from $line]] >= 0} { # Change for the 'to' replacement set line [string replace $line $idx [expr {$idx+$fl-1}] $to]
# Stop if we terminate, otherwise note that we've more work to do
set any $more
break; # Restart search for rules to apply } }
#DEBUG# puts $line }
# Output the processed line puts $out $line
} close $out</lang> In the case where there are no terminating rules and no overlapping issues, the following is an alternative: <lang tcl>package require Tcl 8.5 if {$argc < 3} {error "usage: $argv0 ruleFile inputFile outputFile"} lassign $argv ruleFile inputFile outputFile
- Read the file of rules
set rules {} set f [open $ruleFile] foreach line [split [read $f] \n[close $f]] {
if {[string match "#*" $line] || $line eq ""} continue
if {[regexp {^(.+)\s+->\s+(.*)$} $line -> from to]} {
dict set rules $from $to
} else {
error "Syntax error: \"$line\""
}
}
- Apply the rules in a simplistic manner
set in [open $inputFile] set out [open $outputFile w] set data [read $in] close $in while 1 {
set newData [string map $rules $data]
if {$newData eq $data} break
set data $newData
} puts $out $data close $out</lang>
VBScript
Implementation
<lang vb> class markovparser
dim aRules public property let ruleset( sBlock ) dim i aRules = split( sBlock, vbNewLine ) '~ remove blank lines from end of array do while aRules( ubound( aRules ) ) = vbnullstring redim preserve aRules( ubound( aRules ) - 1 ) loop '~ parse array for i = lbound( aRules ) to ubound( aRules ) if left( aRules( i ), 1 ) = "#" then aRules( i ) = Array( vbnullstring, aRules(i)) else aRules( i ) = Split( aRules( i ), " -> ", 2 ) end if next end property
public function apply( sArg ) dim ruleapplied dim terminator dim was dim i dim repl dim changes
ruleapplied = true terminator = false
do while ruleapplied and (not terminator) changes = 0 was = sArg for i = lbound( aRules ) to ubound( aRules ) repl = aRules(i)(1) if left( repl, 1 ) = "." then terminator = true repl = mid( repl, 2 ) end if sArg = replace( sArg, aRules(i)(0), repl) if was <> sArg then changes = changes + 1 if changes = 1 then exit for end if end if if terminator then exit for end if next if changes = 0 then ruleapplied = false end if loop apply = sArg end function
sub dump dim i for i = lbound( aRules ) to ubound( aRules ) wscript.echo eef(aRules(i)(0)=vbnullstring,aRules(i)(1),aRules(i)(0)& " -> " & aRules(i)(1)) & eef( left( aRules(i)(1), 1 ) = ".", " #terminator", "" ) next end sub
private function eef( bCond, sExp1, sExp2 ) if bCond then eef = sExp1 else eef = sExp2 end if end function end class </lang>
Invocation
<lang vb> dim m1 set m1 = new markovparser m1.ruleset = "# This rules file is extracted from Wikipedia:" & vbNewLine & _ "# http://en.wikipedia.org/wiki/Markov_Algorithm" & vbNewLine & _ "A -> apple" & vbNewLine & _ "B -> bag" & vbNewLine & _ "S -> shop" & vbNewLine & _ "T -> the" & vbNewLine & _ "the shop -> my brother" & vbNewLine & _ "a never used -> .terminating rule" wscript.echo m1.apply( "I bought a B of As from T S.")
dim m2 set m2 = new markovparser m2.ruleset = replace( "# Slightly modified from the rules on Wikipedia\nA -> apple\nB -> bag\nS -> .shop\nT -> the\nthe shop -> my brother\na never used -> .terminating rule", "\n", vbNewLine ) '~ m1.dump wscript.echo m2.apply( "I bought a B of As from T S.")
dim m3 set m3 = new markovparser m3.ruleset = replace("# BNF Syntax testing rules\nA -> apple\nWWWW -> with\nBgage -> ->.*\nB -> bag" & vbNewLine & _ "->.* -> money\nW -> WW\nS -> .shop\nT -> the\nthe shop -> my brother\na never used -> .terminating rule", "\n", vbNewLine ) wscript.echo m3.apply("I bought a B of As W my Bgage from T S.")
set m4 = new markovparser m4.ruleset = "### Unary Multiplication Engine, for testing Markov Algorithm implementations" & vbNewLine & _ "### By Donal Fellows." & vbNewLine & _ "# Unary addition engine" & vbNewLine & _ "_+1 -> _1+" & vbNewLine & _ "1+1 -> 11+" & vbNewLine & _ "# Pass for converting from the splitting of multiplication into ordinary" & vbNewLine & _ "# addition" & vbNewLine & _ "1! -> !1" & vbNewLine & _ ",! -> !+" & vbNewLine & _ "_! -> _" & vbNewLine & _ "# Unary multiplication by duplicating left side, right side times" & vbNewLine & _ "1*1 -> x,@y" & vbNewLine & _ "1x -> xX" & vbNewLine & _ "X, -> 1,1" & vbNewLine & _ "X1 -> 1X" & vbNewLine & _ "_x -> _X" & vbNewLine & _ ",x -> ,X" & vbNewLine & _ "y1 -> 1y" & vbNewLine & _ "y_ -> _" & vbNewLine & _ "# Next phase of applying" & vbNewLine & _ "1@1 -> x,@y" & vbNewLine & _ "1@_ -> @_" & vbNewLine & _ ",@_ -> !_" & vbNewLine & _ "++ -> +" & vbNewLine & _ "# Termination cleanup for addition" & vbNewLine & _ "_1 -> 1" & vbNewLine & _ "1+_ -> 1" & vbNewLine & _ "_+_ -> " '~ m4.dump wscript.echo m4.apply( "_1111*11111_")
set fso = createobject("scripting.filesystemobject") set m5 = new markovparser m5.ruleset = fso.opentextfile("busybeaver.tur").readall wscript.echo m5.apply("000000A000000") </lang>
Output
<lang vb> I bought a bag of apples from my brother. I bought a bag of apples from T shop. I bought a bag of apples with my money from T shop. 11111111111111111111 00011H1111000 </lang>
zkl
<lang zkl>fcn parseRuleSet(lines){
if(vm.numArgs>1) lines=vm.arglist; // lines or object
ks:=L(); vs:=L();
foreach line in (lines){
if(line[0]=="#") continue; // nuke <comment>
pattern,replacement:=line.replace("\t"," ")
.split(" -> ",1).apply("strip");
ks.append(pattern); vs.append(replacement);
}
return(ks,vs);
}
fcn markov(text,rules){
ks,vs:=rules; eks:=ks.enumerate();
do{ go:=False;
foreach n,k in (eks){
if (Void!=text.find(k)){ if (Void==(v:=vs[n])) return(text); if (v[0,1]==".") v=v[1,*] else go=True; text=text.replace(k,v,1); break; // restart after every rule application, unless terminating }
} }while(go); text
}</lang> <lang zkl>ruleSet:=parseRuleSet("# This rules file is extracted from Wikipedia:",
"# http://en.wikipedia.org/wiki/Markov_Algorithm", "A\t->\tapple", "B -> bag", "S -> shop", "T -> the", "the shop -> my brother", "a never used -> .terminating rule");
ruleSet.println(); markov("I bought a B of As from T S.",ruleSet).println();</lang>
- Output:
L(L("A","B","S","T","the shop","a never used"),L("apple","bag","shop","the","my brother",".terminating rule"))
I bought a bag of apples from my brother.
<lang zkl>parseRuleSet( // rule set in a list
T("# Slightly modified from the rules on Wikipedia",
"A -> apple", "B -> bag", "S -> .shop", "T -> the",
"the shop -> my brother", "a never used -> .terminating rule")) :
markov("I bought a B of As from T S.",_).println();
parseRuleSet("# BNF Syntax testing rules", "A -> apple",
"WWWW -> with", "Bgage -> ->.*", "B -> bag", "->.* -> money", "W -> WW", "S -> .shop", "T -> the", "the shop -> my brother", "a never used -> .terminating rule") :
markov("I bought a B of As W my Bgage from T S.",_).println();</lang>
- Output:
I bought a bag of apples from T shop. I bought a bag of apples with my money from T shop.
For the next two tasks, read the rule set from a file. <lang zkl>parseRuleSet(File("ruleSet4")) : markov("_1111*11111_",_).println(); parseRuleSet(File("ruleSet5")) : markov("000000A000000",_).println();</lang>
- Output:
11111111111111111111 00011H1111000
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