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发布时间:2020-12-13 22:20:31 所属栏目:PHP教程 来源:网络整理
导读:$a = ((0.1 + 0.7) * 10) == (int)((0.1 + 0.7) * 10); PHP返回false. 任何人都可以解释一下,为什么会这样? 首先返回8,第二个7. 解决方法 引用 big fat red warning in the PHP Manual on Floating Point Precision: It is typical that simple decimal fr
$a = ((0.1 + 0.7) * 10) == (int)((0.1 + 0.7) * 10);

PHP返回false.

任何人都可以解释一下,为什么会这样?
首先返回8,第二个7.

解决方法

引用 big fat red warning in the PHP Manual on Floating Point Precision:

It is typical that simple decimal fractions like 0.1 or 0.7 cannot be converted into their internal binary counterparts without a small loss of precision. This can lead to confusing results: for example,floor((0.1+0.7)*10) will usually return 7 instead of the expected 8,since the internal representation will be something like 7.9.

This is due to the fact that it is impossible to express some fractions in decimal notation with a finite number of digits. For instance,1/3 in decimal form becomes 0.3.

So never trust floating number results to the last digit,and never compare floating point numbers for equality. If higher precision is necessary,07001 and 07002 functions are available.

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