++ / - 具有浮点数和双精度数的运算符 [英] ++ / -- operators with floats and doubles

问题描述

昨天我在一段代码中发现一个浮点数用++递增。

出于某种原因（错误，我猜......）我认为只有整数类型

可以这样递增，我从未见过浮动或双打

之前增加。只是为了确保我做了一个玩具程序和

用gcc -ansi -pedantic -Wall编译，它没有任何错误

或警告，显示正确的结果。

用++和 - 增加浮点数或双精度是否正确？是定义了
还是我进入了未定义行为的领域？如果它是正确的，那你能想到一个有用的地方吗？

非常感谢你的时间，

Al

Yesterday I found in a piece of code a float being incremented with ++.
For some reason (wrong, I guess...) I thought that only integer types
could be incremented that way, and I had never seen floats or doubles
incremented that way before. Just to be sure I did a toy program and
compiled with gcc -ansi -pedantic -Wall and it worked without any error
or warning, showing the correct result.
Is it correct to increment floats or doubles with ++ and --? Is it
defined or am I getting into the realm of undefined behaviour? If it''s
correct, can you think of a place where it could be useful?
Many thanks for your time,
Al

推荐答案

我的************** @ gmail.com 写道：

my**************@gmail.com wrote:

用+增加浮点数或加倍数是否正确+和 - ？它是定义还是我进入未定义行为的领域？


任何标量类型都可以递增。

你也可以增加指针。

如果它是
是的，你能想到一个有用的地方吗？

Is it correct to increment floats or doubles with ++ and --? Is it
defined or am I getting into the realm of undefined behaviour?
Any scalar type may be incremented.
You can also increment pointers.
If it''s
correct, can you think of a place where it could be useful?

任何时候你可能想要将浮点数的值增加一个。

可能会发生，对吗？


-

pete

Any time that you might want to increase the value of a float by one.
It could happen, right?

--
pete

>任何时候你可能想要将浮点数的值增加一个。

> Any time that you might want to increase the value of a float by one.

它可能会发生，对吧？

我认为这个问题浮动就是这个，取决于浮动的大小，它可能是一个noop。


Jon

- -

学习使用Linux汇编语言进行编程
http://www.cafeshops.com/bartlettpublish.8640017

" Jonathan Bartlett" <乔***** @ eskimo.com>写了

"Jonathan Bartlett" <jo*****@eskimo.com> wrote

任何时候你可能想要将浮点数的值增加一个。
它可能会发生，对吧？

Any time that you might want to increase the value of a float by one.
It could happen, right?

我认为浮动的问题在于，取决于浮动的大小，它可能是一个noop。

I think the problem with floats is that, depending on the magnitude of the
float, it may be a noop.

另一个问题是添加一个与递增是不一样的。

递增就是你在计算时所做的，增加一个就是加一个常数

恰好是统一的。

所以，如果我计算观众，因为他们将十字转门传递给一场足球比赛，那就说明了

count ++

每次有人通过时。

另一方面，目前的规则是胜利是3分，而

平局是一分，亏损没有分。如果（goalfor == goalagainst）

积分++;

这应该是

是不对的。要点+ = 1;

要明确1是一个可以改变的外部定义的常数。

规则可能会改变，因此平局得分为零而损失为例如，减去

一个。


浮点数值通常不用于计数，这就是我们

有整数。因此增加它们通常没有意义。

The other problem is that adding one isn''t the same as incrementing.
Incrementing is what you do when you count, adding one is adding a constant
that happens to be unity.
So if I am counting spectators as they pass throught he turnstiles to a
football match, it makes sense to say
count++
every time someone passes through.
On the other hand current rules are that a win is three points, whilst a
draw is one point, and a loss no points. It is not right to say
if(goalsfor == goalsagainst)
points++;
It should be
points += 1;
To make clear that 1 is an externally-defined constant that could change.
The rules could change so that a draw scores zero whilst a loss is minus
one, for example.

Floating point values aren''t generally used for counting, that''s what we
have integers for. So it doesn''t usually make sense to increment them.

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