Question

我一直认为当浮点数被截断为整数时，它总是变成小于浮点数的最大数字。但是，当float在-0.5和0之间时，它将转换为0而不是-1！为什么是这样？这种语言特定吗？我在objC中看到了这一点。

Answer 1

嗯，简短的回答是你的理解实际上是正确的：

0是一个大于-1的数字。

更长或更详细的答案取决于浮点数如何转换为整数。如果你希望“-1”而不是“0”表示浮点数为“0.5”，你可能需要编写自己的实现来剥离浮动的负数，将其向上或向下舍入为整数，然后添加（或乘以a -1，确切地说是负号。回到它上面。

以下是我编写的一些代码，用于演示实现中的差异：

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{

    @autoreleasepool {

        // insert code here...
        NSLog(@"Hello, World!");
        float floatNumber = -1.0f;
        for(NSInteger index = 0; index < 20; index++)
        {
            NSLog( @"floatNumber is %4.2f and integer is %d %d", floatNumber, (int) floatNumber, (int)roundf(floatNumber));
            floatNumber+=0.1f;
        }
    }
    return 0;
}

在Xcode下，结果如下：

floatNumber is -1.00 and integer is -1 -1
floatNumber is -0.90 and integer is 0 -1
floatNumber is -0.80 and integer is 0 -1
floatNumber is -0.70 and integer is 0 -1
floatNumber is -0.60 and integer is 0 -1
floatNumber is -0.50 and integer is 0 0
floatNumber is -0.40 and integer is 0 0
floatNumber is -0.30 and integer is 0 0
floatNumber is -0.20 and integer is 0 0
floatNumber is -0.10 and integer is 0 0
floatNumber is 0.00 and integer is 0 0
floatNumber is 0.10 and integer is 0 0
floatNumber is 0.20 and integer is 0 0
floatNumber is 0.30 and integer is 0 0
floatNumber is 0.40 and integer is 0 0
floatNumber is 0.50 and integer is 0 1
floatNumber is 0.60 and integer is 0 1
floatNumber is 0.70 and integer is 0 1
floatNumber is 0.80 and integer is 0 1
floatNumber is 0.90 and integer is 0 1

当将float转换为int时，为什么数字＆gt; -1和＆lt; -0.5转到-1，数字＆gt; = -0.5和＆lt; 0转到0？

1 个答案: