290:(however, it has been shown that Befunge-93 is Turing Complete with unbounded stack word size). The later Funge-98 specification provides Turing completeness by removing the size restrictions on the program; rather than wrapping around at a fixed limit, the movement of a Funge-98 instruction pointer follows a model dubbed "Lahey-space" after its originator, Chris Lahey. In this model, the grid behaves like a torus of finite size with respect to wrapping, while still allowing itself to be extended indefinitely.
325:: each instruction is compiled to a snippet of C code, and control flows through the snippets just as it does in a Befunge interpreter (that is, conditionally on the value of some 'direction' register). This does not result in a significant advantage over a good interpreter. Note that the bef2c compiler is not correct since it does not handle either 'p' or string mode, but it would not be impossible to make it do so (although the C language might not be well-suited for this).
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As stated, the design goal for
Befunge was to create a language which was difficult to compile. This was attempted with the implementation of self-modifying code (the 'p' instruction can write new instructions into the playfield) and a multi-dimensional playfield (the same instruction can be executed
230:
The name "Befunge" originated from a typing error in an online discussion. While it was designed to be difficult to compile, compilers such as bef2c and Betty have managed to implement the language using various techniques. Befunge programs are characterized by their use of arrows to change control
226:
Befunge was created by Chris
Pressey in 1993 for the Amiga. The language was designed to be as hard to compile as possible, featuring self-modifying code and a multi-dimensional playfield. Despite this, several compilers have been written for the language. The original Befunge-93 specification
215:. It differs from conventional languages in that programs are arranged on a two-dimensional grid. "Arrow" instructions direct the control flow to the left, right, up or down, and loops are constructed by sending the control flow in a cycle. It has been described as "a cross between
411:
order and output as text characters to give "Hello". A space is character number 32 in ASCII, which here is constructed by multiplying 4 and 8, before being output as text. The remaining code then outputs "World!" in a similar way, followed by ASCII character 10 (a
340:
The technique of using arrows to change control flow is demonstrated in the random number generator program below. The
Befunge instruction pointer begins in the upper left corner and will travel to the right if not redirected. Following the arrows around, the
499:!dlrow ,olleHH"). Then the "_" operation will pop the duplicated value, and go right if it's a zero, left otherwise. (This assumes a compliant interpreter that "returns" 0 when popping an empty stack.) When it goes left, it pops and prints the top value as an
255:. Nevertheless, a number of compilers have subsequently been written. A number of extensions to the original "Befunge-93" specification also exist, most notably Funge-98, which extends the concept to an arbitrary number of dimensions and can be
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character. It then duplicates the next character and loops back to the "_" test, continuing to print the rest of the stack until it is empty and so the next value popped is 0, at which point "@" ends the program.
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treat strings as comments in contexts where the values are not used. Similarly, in
Befunge, there is no comment syntax: to embed documentation in the code, the programmer simply routes the control flow
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The etty compiler, for example, treats every possible straight line of instructions as a subprogram, and if a 'p' instruction alters that subprogram, that subprogram is recompiled. This variation on
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results in a much better advantage over an interpreter, since many instructions can be executed in native code without making intervening decisions on the 'direction' register.
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The
Befunge-93 specification restricts each valid program to a grid of 80 instructions horizontally by 25 instructions vertically. Program execution which exceeds these limits
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instructions send the instruction pointer in random cardinal directions until the pointer hits a digit, pushing it to the stack. Then the arrows navigate to the
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ordering means that "H" is now the top of the stack and will be the first printed, "e" is second, and so on. To print the characters, the program enters a
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limited programs to an 80x25 grid, and while not Turing-complete, subsequent extensions like Funge-98 expanded the concept to achieve Turing completeness.
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Nevertheless, these obstacles have been overcome, to some degree, and
Befunge compilers have been written using appropriate techniques.
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to output the digit from the stack and return the pointer to the first directional randomiser. There is no
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flow, and they can produce outputs like random number sequences or classic "Hello, World!" messages.
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The following code is a slightly more complicated version. It adds the ASCII character 10 (a
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to a corresponding point on the other side of the grid; a
Befunge program is in this manner
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to terminate this program, so it produces an endless stream of random numbers from 1 to 9.
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operating simultaneously on the same space. Befunge-extensions and variants are called
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Most one-dimensional programming languages require some syntactic distinction between
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that first duplicates the top value on the stack (so now the stack would look like "
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Start string mode: push each character's ASCII value all the way up to the next
35:
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Logical NOT: Pop a value. If the value is zero, push 1; otherwise, push zero.
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character) to the stack, and then pushes "!dlrow ,olleH" to the stack. Again,
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The bef2c compiler included with the standard
Befunge-93 distribution uses
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the "comment" area, so that the text in that area is never executed.
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The language was originally created by Chris
Pressey in 1993 for the
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404:
283:
240:
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in an online discussion, where the word 'before' was intended.
29:
873:
A "put" call (a way to store a value for later use). Pop
403:. First the letters "olleH" are pushed onto the stack as
243:, as an attempt to devise a language which is as hard to
1009:– PlayStation programming game using a similar language
843:
Pop value and output as an integer followed by a space
906:
A "get" call (a way to retrieve data in storage). Pop
676:, then push the remainder of the integer division of
416:
character, moving the output cursor to a new line).
893:) in the program to the character with ASCII value
780:Pop a value; move right if value=0, left otherwise
182:
162:
147:
137:
60:. Unsourced material may be challenged and removed.
934:Ask user for a character and push its ASCII value
971:— although that distinction may be as trivial as
407:numbers. These are then popped from the stack in
790:Pop a value; move down if value=0, up otherwise
399:The following code is an example of the classic
1184:
8:
770:Start moving in a random cardinal direction
132:
1110:: CS1 maint: numeric names: authors list (
27:2-dimensional esoteric programming language
1191:
1177:
1169:
975:'s rule that any character not in the set
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120:Learn how and when to remove this message
853:Pop value and output as ASCII character
833:Pop value from the stack and discard it
1326:Non-English-based programming languages
1039:
1103:
1331:Programming languages created in 1993
7:
1321:Stack-oriented programming languages
823:Swap two values on top of the stack
813:Duplicate value on top of the stack
58:adding citations to reliable sources
1159:Befunge-93 Reference Implementation
924:Ask user for a number and push it
25:
557:Push this number onto the stack.
1292:
1291:
1271:Shakespeare Programming Language
885:, then change the character at (
34:
315:in four different directions).
45:needs additional citations for
1316:Esoteric programming languages
1200:Esoteric programming languages
1:
979:is a comment. Languages like
213:esoteric programming language
1261:One-instruction set computer
1064:. 1997-11-04. Archived from
545:Befunge-93 instruction list
247:as possible. Note that the
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1289:
1206:
551:
518:"!dlrow ,olleH"
187:
1154:Befunge-93 Specification
506:
418:
355:
330:just-in-time compilation
863:Bridge: Skip next cell
1164:Funge-98 Specification
642:Integer division: Pop
401:"Hello World!" program
358:v>>>>>v
336:Sample Befunge-93 code
1125:Oerjan (2014-01-18).
1086:Ais523 (2008-12-18).
1062:"The Befunge FAQ v.4"
658:, rounded towards 0.
203:is a two-dimensional
617:Multiplication: Pop
261:instruction pointers
54:improve this article
1048:"Befunge – Esolang"
730:Start moving right
253:self-modifying code
251:command allows for
148:First appeared
134:
760:Start moving down
740:Start moving left
720:, otherwise zero.
704:Greater than: Pop
460:"World!"
302:is derived from a
1303:
1302:
961:
960:
712:, then push 1 if
592:Subtraction: Pop
433:"Hello"
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16:(Redirected from
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1088:"Chris Pressey"
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1148:External links
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567:Addition: Pop
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276:"wraps around"
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1068:on 2001-04-17
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323:threaded code
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281:
280:topologically
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257:multithreaded
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183:Influenced by
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143:Chris Pressey
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88:
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81:
78:
74:
71: –
70:
66:
65:Find sources:
59:
55:
49:
48:
43:This article
41:
37:
32:
31:
19:
18:Chris Pressey
1236:Iota and Jot
1215:
1134:. Retrieved
1130:
1120:
1095:. Retrieved
1091:
1081:
1070:. Retrieved
1066:the original
1056:
1042:
989:
977:+-<>,.
965:comment text
962:
944:End program
911:
907:
894:
890:
886:
882:
878:
874:
717:
713:
709:
705:
681:
677:
673:
669:
668:Modulo: Pop
655:
651:
650:, then push
647:
643:
630:
626:
625:, then push
622:
618:
605:
601:
600:, then push
597:
593:
580:
576:
575:, then push
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568:
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398:
339:
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317:
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304:typing error
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238:
229:
225:
200:
199:
116:
110:January 2012
107:
97:
90:
83:
76:
64:
52:Please help
47:verification
44:
969:source code
310:Compilation
205:stack-based
174:/Befunge-93
1310:Categories
1281:Whitespace
1136:2014-01-23
1097:2014-01-23
1072:2014-01-23
1034:References
1018:Whitespace
209:reflective
80:newspapers
1221:Brainfuck
1002:Brainfuck
973:Brainfuck
485:line feed
414:line feed
298:The word
294:Etymology
265:Fungeoids
139:Developer
69:"Befunge"
1297:Category
1276:Unlambda
1256:Malbolge
1231:INTERCAL
1226:FRACTRAN
1106:cite web
1023:Malbolge
1013:INTERCAL
996:See also
267:or just
221:Lemmings
1251:LOLCODE
1216:Befunge
1211:Beatnik
1131:Esolang
1092:Esolang
951:(space)
300:Befunge
245:compile
235:History
201:Befunge
168:catseye
163:Website
153: (
133:Befunge
94:scholar
1241:JSFuck
990:around
985:Python
881:, and
457:,,,,,,
269:Funges
96:
89:
82:
75:
67:
955:No-op
920:&
501:ASCII
430:,,,,,
405:ASCII
361:12345
284:torus
241:Amiga
217:Forth
193:FALSE
189:Forth
176:.html
172:/node
101:JSTOR
87:books
1266:Piet
1246:Leet
1112:link
1028:Piet
983:and
981:Lisp
967:and
910:and
736:<
726:>
716:>
708:and
672:and
646:and
621:and
596:and
571:and
536:>
509:>
493:loop
489:LIFO
466:>
463:<
439:>
436:<
421:>
409:LIFO
394:<
379:6789
367:>
219:and
155:1993
151:1993
73:news
553:0-9
376:v?v
364:^?^
223:".
170:.tc
56:by
1312::
1129:.
1108:}}
1104:{{
1090:.
877:,
829:$
684:.
533:_@
530::,
512:25
497:\n
469:25
442:48
373:?^
271:.
211:,
207:,
191:,
1192:e
1185:t
1178:v
1139:.
1114:)
1100:.
1075:.
1050:.
940:@
930:~
912:x
908:y
902:g
895:v
891:y
889:,
887:x
883:v
879:x
875:y
869:p
859:#
849:,
839:.
819:\
809::
802:"
796:"
786:|
776:_
766:?
756:v
746:^
718:a
714:b
710:b
706:a
700:`
690:!
682:a
680:/
678:b
674:b
670:a
664:%
656:a
654:/
652:b
648:b
644:a
638:/
631:b
629:*
627:a
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619:a
613:*
606:a
604:-
602:b
598:b
594:a
588:-
581:b
579:+
577:a
573:b
569:a
563:+
539:^
527:v
524:v
521::
515:*
478:@
475:,
472:*
454:v
451:v
448:,
445:*
427:v
424:v
391:.
388:^
385:v
370:?
351:@
347:.
343:?
249:p
157:)
123:)
117:(
112:)
108:(
98:·
91:·
84:·
77:·
50:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
