检查预置双精度值的有效性 [英] Validity of checking exact value of preset double

问题描述

我有时在我的代码中执行以下操作，当我懒惰：

  double d = 0; 
 ... 
 if（condition1）d = 1.0; 
 
 ... 
 if（d == 0）{//不确定这是否有效
} 
   double 为 0的事实，p $ p> 
 $ b 我可以稍后用 d == 0 可靠地检查代码吗？ 
 
 
 
我理解，如果我在上面的代码中对 d 进行计算，我不能期望 d 正好 0 但如果我设置它，我会认为我可以。 
解决方案
是的，对于大多数情况（即不包括NaN ）：在赋值 a = b; 之后，条件 a == b 为true。因此，只要你只分配和比较你分配的东西，这应该是可靠的，即使对于浮点类型。
 
I sometimes do the following in my code when I am being lazy:
double d = 0;
 ...
if( condition1 ) d = 1.0;

...
if (d == 0) { //not sure if this is valid
}
can I always count on the fact that if I set a double to be 0 I can later check in the code for it with d == 0 reliably? 

I understand that if I do computations on d in the above code, I can never expect d to be exactly 0 but if I set it, I would think I can. All my testing so far on various systems seem to indicate that this is legitimate.
解决方案
Yes, for most cases (i.e. excluding NaN): After the assignment a = b; the condition a == b is true. So as long as you're only assigning and comparing to the thing you assign from, this should be reliable, even for floating-point types.

                        
这篇关于检查预置双精度值的有效性的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！