Objective-c 中的计算未返回正确的值
请查看这段代码，更具体地说是 hourStep 计算。
int h = [[timeArray objectAtIndex:0] intValue];
int m = [[timeArray objectAtIndex:1] intValue];
int s = [[timeArray objectAtIndex:2] intValue];
int mm = [[timeArray objectAtIndex:3] intValue];
NSLog([NSString stringWithFormat:@"time h:%d, m:%d, s:%d, mm:%d", h, m, s, mm]);
//time h:13, m:7, s:55, mm:105
float hourStep1 = m / 60;
float hourStep2 = h + hourStep1;
float hourStep3 = hourStep2 / 24;
float hourStep4 = hourStep3 * 15;
int hour1 = ceil(hourStep4);
NSLog([NSString stringWithFormat:@"hourStep1: %f, hourStep2: %f, hourStep3: %f, hourStep4: %f result: %d", hourStep1, hourStep2, hourStep3, hourStep4, hour1]);
//hourStep1: 0.000000, hourStep2: 13.000000, hourStep3: 0.541667, hourStep4: 8.125000 result: 9
float hourStep5 = ((h + (m / 60)) / 24) * 15;
NSLog([NSString stringWithFormat:@"hourStep5: %f", hourStep5]);
//hourStep5: 0.000000
我已将计算分解为各个步骤以获得正确答案，但是任何人都可以解释为什么 hourStep5 不会产生 hourStep4 产生的结果吗？
Please check out this piece of code, more specifically the hourStep calculations.
int h = [[timeArray objectAtIndex:0] intValue];
int m = [[timeArray objectAtIndex:1] intValue];
int s = [[timeArray objectAtIndex:2] intValue];
int mm = [[timeArray objectAtIndex:3] intValue];
NSLog([NSString stringWithFormat:@"time h:%d, m:%d, s:%d, mm:%d", h, m, s, mm]);
//time h:13, m:7, s:55, mm:105
float hourStep1 = m / 60;
float hourStep2 = h + hourStep1;
float hourStep3 = hourStep2 / 24;
float hourStep4 = hourStep3 * 15;
int hour1 = ceil(hourStep4);
NSLog([NSString stringWithFormat:@"hourStep1: %f, hourStep2: %f, hourStep3: %f, hourStep4: %f result: %d", hourStep1, hourStep2, hourStep3, hourStep4, hour1]);
//hourStep1: 0.000000, hourStep2: 13.000000, hourStep3: 0.541667, hourStep4: 8.125000 result: 9
float hourStep5 = ((h + (m / 60)) / 24) * 15;
NSLog([NSString stringWithFormat:@"hourStep5: %f", hourStep5]);
//hourStep5: 0.000000
I have broken down the calculation into the various steps to get the correct answer but can anyone explain why hourStep5 doesn't produce what hourStep4 produces?
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这就是整数除法和浮点除法的区别。
此行：
计算结果为
13.0f / 24，结果为0.541667f（浮点除法）。在组合计算中，您仅处理整数（不转换为中间的浮点数），因此
计算结果为
13 / 24，等于0（整数除法）。将其更改为，您将得到与上面相同的结果。
It's the difference between integer division and floating-point division.
This line:
evaluates to
13.0f / 24which results in0.541667f(floating-point division).In the combined calculation, you are only dealing with integers (without converting to floats in between), so
evaluates to
13 / 24which equals0(integer division). Change it toand you will get the same result as above.
在你的行中
计算是在
int中执行的，而不是在float中执行的。请注意，在 C 中（因此在 Objective-C 中）首先执行=右侧的方程，而不关心左侧的类型（在本例中为浮动。）请改用
。
In your line
The calculation is performed in
int, not infloat. Note that in C (and thus in Objective-C) the equation on the right hand side of=is performed first, without caring whatsoever the type of the left hand side (in this case,float.)Use
instead.
hourStep5 的整个计算将被视为整数。
尝试将 h 和 m 都转换为该行中的浮点数：
The whole calculation of hourStep5 will be treated as integer.
Try casting both h and m into floats in that line: