Brainfuck language transpiler to Emacs Lisp
The brainfuck language transpiler to Emacs Lisp consists of ebf
macro which expands to the actual Emacs Lisp code. Here is the
signature of this macro:
(ebf INPUT-CALLBACK OUTPUT-CALLBACK &rest INSTRUCTIONS)
INPUT-CALLBACK is called on comma instruction and should have zero
arguments and return a number.
OUTPUT-CALLBACK is called on dot instruction and should have one
argument of an integer type.
INSTRUCTIONS is a list of symbols and vectors of symbols. Vectors
are accepted so we don’t need to escape square brackets of our
brainfuck program. Symbols’ names should be sequences of valid
brainfuck instructions excluding square brackets.
Evaluation of the macro expansion causes the brainfuck program execution.
So the code
(ebf input output \,+++[->+<].)will be expanded to
(let ((MEMORY68087 (make-vector 100 0))
(POINTER68088 0)
(INPUT68085 input)
(OUTPUT68086 output))
(aset MEMORY68087 POINTER68088 (funcall INPUT68085))
(cl-incf (aref MEMORY68087 POINTER68088) 3)
(while (not (zerop (aref MEMORY68087 POINTER68088)))
(cl-decf (aref MEMORY68087 POINTER68088) 1)
(cl-incf POINTER68088 1)
(while (<= (length MEMORY68087) POINTER68088)
(let ((memory-length (length MEMORY68087)))
(setq MEMORY68087
(vconcat MEMORY68087
(make-vector
(max 1 (/ memory-length 2))
0)))))
(cl-incf (aref MEMORY68087 POINTER68088) 1)
(cl-decf POINTER68088 1))
(funcall OUTPUT68086 (aref MEMORY68087 POINTER68088)))We collapse several instructions in a row and automatically expand the memory to the right. We plan to add more optimization in the future.
Here is the classical Hello World example with some output:
(require 'ebf)
(let ((result nil))
(ebf nil #'(lambda (x) (push x result))
++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++
.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.
------.--------.>+.>.)
(apply #'string (reverse result)));<- put cursor here and press C-x C-eebf macro produces the code that doesn’t depend on ebf module
itself. That means we can byte-compile our brainfuck programs so they
will not require ebf at runtime.
Check Macros and Byte Compilation section of the official Emacs Lisp manual on how to do that.
Basically we will need to wrap our (require 'ebf) with
eval-when-compile like
(eval-when-compile
(require 'ebf))Copyright (C) 2015 Alexey Kutepov a.k.a rexim
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.