什么小于0。(0点)的意思吗?(复制)

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这个问题已经有了答案:

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I just saw this for the first time. The source code I'm looking at is in C

我是第一次看到这个。我正在查看的源代码在C语言中

 if( rate < 0.){
   ...
 }
 else{
   ...
 }

What happens if rate=0 ?

如果速率为0会怎样?

3 个解决方案

#1

0. is a literal of type double (and value zero). By contrast, 0 is a literal of type int.

0。是double类型的文字(值为0)。相比之下，0是int类型的文字。

#2

It is interpreting 0. as a double (0.0) instead of an integer (0).

这是解释0。作为一个double(0.0)而不是整数(0)。

Check the link: of "working code", showing the different sizes of various types of zero constants:

查看“工作代码”的链接，显示各种类型的零常量的不同大小:

#3

0. is a floating constant and since it does not have a suffix it is a double, from the draft C99 standard section 6.4.4.2 Floating constants we have the following grammar:

0。是一个浮动常数，由于没有后缀，所以是双精度浮点数，从C99标准章节6.4.4.2浮动常数的草稿来看，我们有以下语法:

floating-constant:
   decimal-floating-constant
   hexadecimal-floating-constant
decimal-floating-constant:
   fractional-constant exponent-part_opt floating-suffix_opt
   digit-sequence exponent-part floating-suffix_opt
[...]
fractional-constant:
    digit-sequence_opt . digit-sequence
    digit-sequence .                                   < ---- This covers 0.
[...]

We then have in paragraph 4:

然后，我们在第4段中:

An unsuffixed floating constant has type double. If suffixed by the letter f or F, it has type float. If suffixed by the letter l or L, it has type long double.

无后缀的浮动常数类型为double。如果后缀是f或f，它有类型float。如果后缀是字母l或l，那么它的类型是long double。

#1