#include <stdio.h>
#include <stdlib.h>
#include <math.h>

double Add( double x, double y )
{
 return x + y;
}

double Sub(double x, double y)
{
 return x - y;
}

double Mul(double x, double y)
{
 return x * y;
}

double Div( double x, double y )
{
 return x / y;
}
//五个函数指针数组，这些函数都需要两个double参数，返回值是double

double (*funcTable[5])(double, double)={Add, Sub, Mul, Div, pow};

char *msgTable[5] = {"Sum", "Difference", "Product", "Quotient", "Power"};

int main()
{
 int i;
 double x = 0, y = 0;

 printf("Enablr two operands for some arithmetic:\n");
 if( scanf("%lf%lf", &x, &y) != 2 )
  printf("Invalid input.\n");

 for(i = 0; i < 5; i++)
 {
  printf("%10s: %6.2f\n", msgTable[i], funcTable[i](x, y));
 }

 return 0;
}
后来想想，还是正规一些，增加程序的可读性，这一定义funcTable比较好看：
typedef double func_t (double, double);
func_t  *funcTable[5] = { Add, Sub, Mul, Div, pow};