gistfile1.c

// file df.c
#include <stdio.h>
#include <math.h>

double dx = 0.0001;

double df(double x, double (*f)(double)) {
  double dy = (*f)(x+dx)-(*f)(x);
  return dy/dx;
}

int main() {
  printf("df(0.5, sin)=%6.2f\n", df(0.5, sin));   
}

/*
D:\ccc\c>gcc -c df.c -o df.o

D:\ccc\c>objdump -d df.o

df.o:     file format pe-i386

Disassembly of section .text:

00000000 <_df>:
   0:   55                      push   %ebp
   1:   89 e5                   mov    %esp,%ebp
   3:   83 ec 18                sub    $0x18,%esp
   6:   dd 45 08                fldl   0x8(%ebp)
   9:   dc 05 00 00 00 00       faddl  0x0
   f:   dd 1c 24                fstpl  (%esp)
  12:   8b 45 10                mov    0x10(%ebp),%eax
  15:   ff d0                   call   *%eax
  17:   dd 5d f0                fstpl  0xfffffff0(%ebp)
  1a:   dd 45 08                fldl   0x8(%ebp)
  1d:   dd 1c 24                fstpl  (%esp)
  20:   8b 45 10                mov    0x10(%ebp),%eax
  23:   ff d0                   call   *%eax
  25:   dc 6d f0                fsubrl 0xfffffff0(%ebp)
  28:   dd 5d f8                fstpl  0xfffffff8(%ebp)
  2b:   dd 45 f8                fldl   0xfffffff8(%ebp)
  2e:   dc 35 00 00 00 00       fdivl  0x0
  34:   c9                      leave
  35:   c3                      ret

00000036 <_main>:
  36:   55                      push   %ebp
  37:   89 e5                   mov    %esp,%ebp
  39:   83 ec 18                sub    $0x18,%esp
  3c:   83 e4 f0                and    $0xfffffff0,%esp
  3f:   b8 00 00 00 00          mov    $0x0,%eax
  44:   83 c0 0f                add    $0xf,%eax
  47:   83 c0 0f                add    $0xf,%eax
  4a:   c1 e8 04                shr    $0x4,%eax
  4d:   c1 e0 04                shl    $0x4,%eax
  50:   89 45 fc                mov    %eax,0xfffffffc(%ebp)
  53:   8b 45 fc                mov    0xfffffffc(%ebp),%eax
  56:   e8 00 00 00 00          call   5b <_main+0x25>
  5b:   e8 00 00 00 00          call   60 <_main+0x2a>
  60:   c7 44 24 08 00 00 00    movl   $0x0,0x8(%esp)
  67:   00
  68:   dd 05 18 00 00 00       fldl   0x18
  6e:   dd 1c 24                fstpl  (%esp)
  71:   e8 8a ff ff ff          call   0 <_df>
  76:   dd 5c 24 04             fstpl  0x4(%esp)
  7a:   c7 04 24 00 00 00 00    movl   $0x0,(%esp)
  81:   e8 00 00 00 00          call   86 <_main+0x50>
  86:   c9                      leave
  87:   c3                      ret
  88:   90                      nop
  89:   90                      nop
  8a:   90                      nop
  8b:   90                      nop
  8c:   90                      nop
  8d:   90                      nop
  8e:   90                      nop
  8f:   90                      nop
*/