为什么模量（％）运算符的工作对于char而不是浮点类型？ [英] Why does modulus (%) operator work for char but not for floating types?

问题描述

#include <stdio.h>

int main()
{
  char c;
  c=10;
  if(c%2==0)
    printf("Yes");
  return 0;
}

以上code打印是。谁能告诉为什么模运算符适用于字符和 INT 而不是双击等。

推荐答案

您已经有了意见，解释为什么％是字符：这是所有整数类型的界定，C，字符是一个整数类型。一些其他的语言作定义，不支持算术运算鲜明的字符类型，但C是不是其中之一。

You already got comments explaining why % is defined for char: it's defined for all integer types, and in C, char is an integer type. Some other languages do define a distinct char type that does not support arithmetic operations, but C is not one of them.

但是，为了回答为什么它不为浮点类型定义：历史。没有任何技术原因为什么不可能定义％运营商浮点类型。这里的C99理由这样说：

But to answer why it isn't defined for floating-point types: history. There is no technical reason why it wouldn't be possible to define the % operator for floating-point types. Here's what the C99 rationale says:

6.5.5乘法运算符

[...]

在C89委员会拒绝延长％运营商浮动类型，这种用法将重复由 FMOD （见§7.12.10.1）。

The C89 Committee rejected extending the % operator to work on floating types as such usage would duplicate the facility provided by fmod (see §7.12.10.1).

和作为mafso后来发现：

And as mafso found later:

7.12.10.1的FMOD功能

[...]

在C89委员会审议使用求余运算符％此功能的建议;但被拒绝，因为一般的运营商对应的硬件设施和 FMOD 硬件不支持大多数机器。

The C89 Committee considered a proposal to use the remainder operator % for this function; but it was rejected because the operators in general correspond to hardware facilities, and fmod is not supported in hardware on most machines.

他们似乎有点矛盾。在％运营商并没有延长，因为 FMOD 已经填补了需求，但 FMOD 被挑来填补这一需求，因为委员会不希望延长％运营商？他们不能很好地同时为真同时

They seem somewhat contradictory. The % operator was not extended because fmod already filled that need, but fmod was picked to fill that need because the committee did not want to extend the % operator? They cannot very well both be true at the same time.

我怀疑这些原因之一是原来的原因，另一个是不晚重新访问该决定的原因，但没有告诉这是第一次。无论哪种方式，它只是决定％不会执行此操作。

I suspect one of these reasons was the original reason, and the other was the reason for not later re-visiting that decision, but there's no telling which was first. Either way, it was simply decided that % wouldn't perform this operation.

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