天热无聊，用C语言函数指针实现的小函数^_^

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
void f_sum(double* ,double*,double*);
void i_sum(int *,int *,int *);
void c_sum(char*,char*,char*);
int main(int argc,char **argv)
{
	int a=10;
	int b=5;
	double c=2.3;
	double d=2.2;
	double fs;
	int is;
	char *ca="Hello ";
	char *cb="World!";
	char *cs;

	void *res=0;

	void (*pfunc) (void*,void*,void*);

	pfunc=f_sum;
	
	pfunc(&c,&d,&fs);
	res=&fs;
	printf("float:result=%.2f
",*(double*)res);
	
	pfunc=i_sum;
	pfunc(&a,&b,&is);
	printf("int:result=%2d
",is);

	pfunc=c_sum;
	cs=malloc(strlen(ca)+strlen(cb)+1);
	memset(cs,0x00,strlen(ca)+strlen(cb)+1);
	pfunc(ca,cb,cs);
	printf("char:result=%s
",cs);
        free(cs);

	return 0;

}

void  f_sum(double *x,double *y,double *z)
{
	*z=(*x)+(*y);
}

void i_sum(int *x,int *y,int *z)
{
	*z=(*x)+(*y);
}

void c_sum(char *x,char *y,char *z)
{
	//memset(z,0x00,strlen(x)+strlen(y));
	sprintf(z,"%s%s",x,y);
}