iOS 另外一个使用类的代码，四则运算，很简单，熟悉以下

//
//  main.m
//  0824-四则运算
//
//  Created by panba on 15-8-24.
//  Copyright (c) 2015年 panba. All rights reserved.
//

#import <Foundation/Foundation.h>
@interface calc:NSObject
-(void) setnum:(double) value;
-(void) clear;
-(double) calcnumreturn;
//算数方法
-(void) calcadd:(double) value;
-(void) calcsub:(double) value;
-(void) calcmul:(double) value;
-(void) calcdiv:(double) value;
@end

@implementation calc
{
double calcnum;
}
-(void) setnum:(double)value
{
calcnum = value;
}
-(void) calcadd:(double)value
{
calcnum = calcnum + value;
}
-(void) calcsub:(double)value
{
calcnum = calcnum - value;
}
-(void) calcdiv:(double)value
{
calcnum = calcnum/value;
}
-(void) calcmul:(double)value
{
calcnum = calcnum*value;
}

-(double) calcnumreturn
{
return calcnum;
}

@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
double value1,value2;
char oper;
calc *calcnum = [[calc alloc] init];
NSLog(@"input");
scanf("%lf %c %lf",&value1,&oper,&value2);
[calcnum setnum:value1];
switch (oper) {
case '+':
[calcnum calcadd:value2];
break;
case '-':
[calcnum calcsub:value2];
break;
case '/':
[calcnum calcdiv:value2];
break;
case '*':
[calcnum calcmul:value2];
break;
default:
NSLog(@"error");
break;
}
[calcnum calcnumreturn];
NSLog(@"%lf",[calcnum calcnumreturn]);
}
return 0;
}