The master programmer "plays" a C program that is not like C

author | Brian Robert Callahan

compile | Zhang Jie

Coordinating editor | Du min

To make the challenge interesting ,Brian Robert Callahan（ Lecturer in information technology and network science at Rensselaer Institute of technology in northern New York ） Decided to write one that doesn't look like C Of C Program . If you put C Language becomes another language , Then write the program in that language , So use C What happens when the compiler compiles the program ？

Can write the following program ,Brian Robert Callahan I think it's a glorious thing .

#include"cpaint.h"


var a, b, c, h, i, l, v, x, y, q, w, p size 65535 ,
packed n size 13 ꞉integer ;


procedure display(r,s,c) ;
begin
  LOOP
    call A(Z) ;
    call H(y,x) ;
    call B(Z)
  POOL ;


  y ꞉＝ r;
  x ꞉＝ s;


  call A(c) ;
  call H(y,x) ;
  call B(c) ;


  call refresh()
end ;


procedure fill(y,x,c,a) ;
begin
  if(y<0 or y>w-1 or x<0 or x>q-1 or c ＝ a or Z ＜＞ a)fill꞉＝ -1 ;


  call draw(c) ;
  call fill(y+1,x,c,a) ;
  call fill(y-1,x,c,a) ;
  call fill(y,x-1,c,a) ;
  call fill(y,x+1,c,a)
end ;


procedure save(r,s) ;
begin
  i ꞉＝ 0 ;
  while(i<13)do
  begin
    n[i] ꞉＝ 0 ;
    i ꞉＝ i+1
  end ;


  call move(w>>1,(q>>1)-6) ;
  call printw("Save: ") ;
  call echo() ;
  call getnstr(n,12) ;
  call noecho() ;


  call open(n,"w+") ;
  call writeChar(83) ;
  call writeChar(w) ;
  call writeChar(q) ;


  LOOP
    call writeChar(Z)
  POOL ;


  y ꞉＝ r;
  x ꞉＝ s;


  call close ;
  call move(y,x)
end ;


procedure load(packed ʌ n) ;
begin
  call open(n,"r") ;
  call check ;


  LOOP
    readln(c);
    call draw(c)
  POOL ;


  c ꞉＝ 0;


  call close
end ;


procedure m() ;
begin
  l ꞉＝ 0 ;
  v ꞉＝ 1 ;


  call A(c) ;
  call H(0,0) ;
  call B(c) ;
  call refresh() ;


  while(v)do
  begin
    read(inp) ;
    '/':l ꞉＝ not l ; if(l)call draw(c) ; OK
    'k':y ꞉＝ y-1 ; if(y<0)y ꞉＝ 0 ; if(l)call draw(c) ; OK
    'j':y ꞉＝ y+1 ; if(y>w-1)y ꞉＝ w-1 ; if(l)call draw(c) ; OK
    'h':x ꞉＝ x-1 ; if(x<0)x ꞉＝ 0 ; if(l)call draw(c) ; OK
    'l':x ꞉＝ x+1 ; if(x>q-1)x ꞉＝ q-1 ; if(l)call draw(c) ; OK
    ' ':call draw(c) ; OK
    'c':c ꞉＝ c+1 ; if(c ＝ M)c ꞉＝ 0 ; OK
    'd':call draw(15) ; OK
    'f':call fill(y,x,c,Z) ; OK
    's':call save(y,x) ; OK
    'q':v ꞉＝ 0 ; OK
    'v':c ꞉＝ c-1 ; if(c ＝ N)c ꞉＝ M-1 ; CALL display(y,x,c)
  end
end ;


procedure main(I c,packed ʌ ʌ v) ;
begin
  call start ;
  call getmaxyx(stdscr,w,q) ;
  if(w>M)w ꞉＝ M ;if(q>M)q ꞉＝ M ;
  call start_color() ;


  while(x<M)do
  begin
    call init_pair(x,x,x) ;
    x ꞉＝ x+1
  end ;


  LOOP
    call draw(15)
  POOL ;


  if(c ＝ 2)call load(v[c-1]) ; call display(0,0,0) ; call m() ; call endwin()
end ;


call main．

Through this code , Maybe many netizens say frankly , This is not C Code , It contains Pascal All the features of language , Use semicolons as statement separators instead of statement terminators , use “:=” Indicates assignment , Maybe some more Algol（ An instruction based programming language ） Of LOOP……POOL grammar . It even has Pascal Return assignment of language , That is, assign a value to the function , Is its return value .

however ,Brian Robert Callahan Explain this , I heard recently that A+、K and Q Language （ They are APL and J Array programming languages like ） The developer of the Arthur Whitney Will use C Preprocessor to create your own language , Then use this self-defined language to realize his language . therefore , He decided to try this interesting experiment .

Brian Robert Callahan be based on PL/0 Custom language for , Write a compiler . The highlight of this exercise is C Compiler will UTF-8 Characters are understood as valid characters of identifiers .Brian Robert Callahan Used a lot to look like ASCII（ American standard code for information exchange ） The characters of , Not really ASCII, Eventually accepted as a valid identifier .C The preprocessor can well convert these identifiers into corresponding instructions . Here you can see the hidden header file .

If you want to see C The real look of the code , Please try to run ：

$ cc -E cpaint.c | clang-format | less

If you're interested , You might as well try the above program ！

Link to the original text ：Brian Robert Callahan