float 与 float 文字比较的奇怪输出 [英] strange output in comparison of float with float literal

问题描述

float f = 0.7;
if( f == 0.7 )
    printf("equal");
else
    printf("not equal");

为什么输出不等于?

为什么会发生这种情况?

Why does this happen?

推荐答案

发生这种情况是因为在你的陈述中

This happens because in your statement

  if(f == 0.7)

0.7 被视为双精度值.尝试 0.7f 以确保将值视为浮点数:

the 0.7 is treated as a double. Try 0.7f to ensure the value is treated as a float:

  if(f == 0.7f)

但正如迈克尔在下面的评论中所建议的那样，您永远不应该测试浮点值是否完全相等.

But as Michael suggested in the comments below you should never test for exact equality of floating-point values.

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