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https://github.com/rexim/ebf

Brainfuck language transpiler to Emacs Lisp
https://github.com/rexim/ebf

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Brainfuck language transpiler to Emacs Lisp

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README 

        
* ebf



Brainfuck language transpiler to Emacs Lisp



** Usage



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:



#+BEGIN_SRC emacs-lisp



(ebf INPUT-CALLBACK OUTPUT-CALLBACK &rest INSTRUCTIONS)



#+END_SRC



~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



#+BEGIN_SRC emacs-lisp

  (ebf input output \,+++[->+<].)

#+END_SRC



will be expanded to



#+BEGIN_SRC emacs-lisp

  (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)))

#+END_SRC



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:



#+BEGIN_SRC emacs-lisp

(require 'ebf)



(let ((result nil))

  (ebf nil #'(lambda (x) (push x result))

       ++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++

       .>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.

       ------.--------.>+.>.)

  (apply #'string (reverse result)));<- put cursor here and press C-x C-e

#+END_SRC



** Compiling ebf



~ebf~ 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 [[http://www.gnu.org/software/emacs/manual/html_node/elisp/Compiling-Macros.html][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



#+BEGIN_SRC emacs-lisp

(eval-when-compile

 (require 'ebf))

#+END_SRC



** License



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.