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尝试编写关于分数运算的简单程序。无法编译代码。在“减法”方法的界面中出现“预期标识符或'（' xcode”错误。

我对这个问题进行了研究，在我看来这是某种通用错误。这是我的程序：

#import <Foundation/Foundation.h>
// Define the Fraction class
@interface Fraction : NSObject
{
int numerator;
int denominator;
}
@property int numerator, denominator;
-(void) print;
-(void) setTo: (int) n over: (int) d;
 -(double) convertToNum;
-(Fraction *) add: (Fraction *) f;
–(Fraction *) subtract: (Fraction *) f;
–(Fraction *) multiply: (Fraction *) f;
–(Fraction *) divide: (Fraction *) f;

-(void) reduce; 
@end

#import "Fraction.h"
@implementation Fraction
@synthesize numerator, denominator;
-(void) print
{
NSLog (@"%i/%i", numerator, denominator);
}
-(double) convertToNum
{
if (denominator != 0)
return (double) numerator / denominator;
else
    return NAN;
}
-(void) setTo: (int) n over: (int) d
{
numerator = n;
denominator = d;
}
// add a Fraction to the receiver

-(Fraction *) add: (Fraction *) f
{

Fraction *result = [[Fraction alloc] init];
result.numerator = numerator * f.denominator +
denominator * f.numerator;
result.denominator = denominator * f.denominator;
[result reduce];
return result;
}

-(Fraction *) subtract: (Fraction *) f
{
Fraction *result = [[Fraction alloc] init];
result.numerator = numerator * f.denominator -
denominator * f.numerator;
result.denominator = denominator * f.denominator;
[result reduce];
return result;
}

-(Fraction *) multiply: (Fraction *) f
{
Fraction *result= [[Fraction alloc] init];

result.numerator = numerator * f.numerator;
result.denominator = denominator * f.denominator;
[result reduce];
return result;

}


-(Fraction *) divide: (Fraction *) f;
{
Fraction *result = [[Fraction alloc] init];
result.numerator= numerator * f.denominator;
result.denominator = denominator * f.numerator;
[result reduce];
return result;
}

-(void) reduce
{
int u = numerator;
int v = denominator;
int temp;
while (v != 0) {
temp = u % v;
u = v;
v = temp;
}
numerator /= u;
denominator /= u;
}
@end
#import "Fraction.h"

int main (int argc, char *argv[])
{
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];


Fraction *myFraction1 = [[Fraction alloc] init];
Fraction *myFraction2 = [[Fraction alloc] init];


[myFraction2 setTo:200 over:300];

[myFraction1 setTo: 100 over: 300];




[myFraction2 subtract: myFraction1];


NSLog (@"The value of myFraction2 is:");

[myFraction2 print];

[myFraction2 release];
[myFraction1 release];

[pool drain];
return 0;
}
4

2 回答 2

2

删除此行末尾的逗号main：

Fraction *myFraction2 = [[Fraction alloc] init], ;
于 2012-09-26T19:36:58.607 回答
0

假设这是文字复制和粘贴，您使用了错误的破折号。最后，在英式和美式键盘上，您想要的键盘位于“0”键的右侧。您似乎正在使用破折号。如果您仔细查看上面的列表，特别是add:与subtract:顶部列表相比，您会发现您的角色稍微宽一些。

尝试复制并粘贴：

-(Fraction *) subtract: (Fraction *) f;

在您现有的定义上查看差异。

于 2012-09-26T19:38:50.663 回答