/******计算器1.0 from Tony*********/
#include<stdio.h>
#include<math.h>
//声明区
void displaymenu(); //main menu
double add(double x,double y);
double sub(double x,double y);
double multi(double x,double y);
double divide(double x,double y);
int arith_compliment(int x,int y);
long int factorial(int n);
int sum_n(int n);
main()
{
int choice;
double tmp1,tmp2;
double result;
while(1)
{
displaymenu();
printf("\n 请选择您需要的计算类型：(1,2,3,4,5,6,7,8)?\n");
scanf("%d",&choice);
switch(choice)
{
case 1:
printf("please input two number to add:"); //加法
scanf("%lf%lf",&tmp1,&tmp2);
result=add(tmp1,tmp2);
printf("%lf+%lf=%lf\n",tmp1,tmp2,result);
break;
case 2:
printf("please input two number to sub:"); //减法
scanf("%lf%lf",&tmp1,&tmp2);
result=sub(tmp1,tmp2);
printf("%lf-%lf=%lf\n",tmp1,tmp2,result);
break;
case 3:
printf("please input two number to multi:"); //乘法
scanf("
