用C語言模仿Python函數(shù)的實例

def line_conf(a, b):
  def line(x):
    return a*x + b
  return line

line1 = line_conf(1, 1)
line2 = line_conf(4, 5)
print(line1(5), line2(5))

/* MIT License

Copyright (c) 2017 Yuandong-Chen

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. */

///////////////////////////////////////////////////////////////////////////////

// Note: The C program is almost equivalent to the Python program as follows:
// def line_conf(a, b):
//   def line(x):
//     return a*x + b
//   return line
//
// line1 = line_conf(1, 1)
// line2 = line_conf(4, 5)
// print(line1(5), line2(5))

#include <stdio.h> 
#include <stdlib.h> 
#include <unistd.h> 
#include <stdarg.h>

typedef int Func();

Func *line_conf(int x, int y,...)
{ 
  va_list ap; 
  va_start(ap, y);

  asm volatile(
    "push %%eax\n\t"
    "subl $40, %%esp\n\t"
    "movl 8(%%ebp), %%eax\n\t"
    "movl %%eax, -36(%%ebp)\n\t"
    "movl 12(%%ebp), %%eax\n\t"
    "movl %%eax, -40(%%ebp)\n\t"
    "addl $40, %%esp\n\t"
    "pop %%eax\n\t"
    :::"memory"
    );

if(va_arg(ap,int) == 1){

LINE:

  asm volatile(
    "push %%ebp\n\t"
    "movl %%esp, %%ebp\n\t"
    "movl 8(%%ebp), %%eax\n\t"
    "imul -36(%%ebp), %%eax\n\t"
    "addl -40(%%ebp), %%eax\n\t"
    "movl %%ebp, %%esp\n\t"
    "pop %%ebp\n\t"
    "ret\n\t"
    :::"memory","%eax"
    );
}  
__END: 
  va_end(ap);
  return (Func *)(&&LINE);
}

int main(int argc, const char *argv[]){ 
  printf("====TEST START====\n");
  printf("34*234+6 ?= %d\n",line_conf(34,6)(234));
  printf("1*3+2 ?= %d; 324*65+3 ?= %d; 13*66+2 ?= %d\n",line_conf(1,2)(3),line_conf(324,3)(65),line_conf(13,2)(66));

  int fd = line_conf(1,6)(4);
  Func *fun = line_conf(3,3);
  int a = 1; // Limited point
  printf("3*3+3 ?= %d; 1*4+6 ?= %d\n",fun(3),fd);
  printf("====TEST END====\n");
  return 0; 
}

// Compile it by the following command:
// gcc -m32 -O0 -fno-stack-protector CFunctional.c; ./a.out
// The terminal output should looks like:
// ====TEST START====
// 34*234+6 ?= 7962
// 1*3+2 ?= 5; 324*65+3 ?= 21063; 13*66+2 ?= 860
// 3*3+3 ?= 12; 1*4+6 ?= 10
// ====TEST END====
//Note: The limitation happens between line 86 and line 88, we cannot insert any function here
// whose stack is larger than 40 bytes.(Why is 40? check the inline assembler language)