blocks|key|1447261|text|这是C%2B%2B+(和C)标准所决定的。浮点文字的类型是double，如果您需要它们是浮点数，可以在它们后面加上一个f。似乎没有任何明确的理由说明原因，但我猜这是a)与C的兼容性，以及b)精度和存储之间的权衡。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1447262|1447263|+2.13.3浮点文字除非由后缀明确指定，否则ﬂoating文字的类型是double。后缀f和F指定浮点数，后缀l和L指定long+double。如果缩放值不在其类型的可表示值范围内，则程序的格式不正确。|blockquote|BOLD|1447264|1447265|entityMap^0|1J|1|0|0|1|A|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]|$1|G|3|H|5|I|7|R|8|@$9|S|A|T|B|J]]|D|@]|E|$]]|$1|K|3|-4|5|6|7|U|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|M|$]]

That's what the C++ (and C) standard decided. Floating point literals are of type double, and if you need them to be floats, you suffix them with a <code>f</code>. There doesn't appear to be any specifically stated reason as to why, but I'd guess it's a) For compatibility with C, and b) A trade-off between precision and storage.

<blockquote>
 2.13.3 Floating literals The type
 of a ﬂoating literal is double unless
 explicitly specified by a suffix. The
 suffixes f and F specify float, the suffixes l and L specify long double.
 If the scaled value is not in the
 range of
 representable values for its type, the program is ill-formed.
</blockquote>

blocks|key|1447277|text|这可能是C语言世界的一个标准。Double是首选，因为它更精确，而且您可能看不到任何性能差异。阅读this+post。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1447278|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/1074474/should-i-use-double-or-float^0|1D|9|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

This is probably a standard in C world. Double is preferred since it's more precise and you probably won't see any performance differences. Read <a href="https://stackoverflow.com/questions/1074474/should-i-use-double-or-float">this post</a>.

blocks|key|191688|text|C和C%2B%2B在几种方式上更喜欢双精度浮点数。正如您注意到的，小数字面量是双精度的，除非显式设置为浮点型。此外，浮点数不能在varargs中传递，它们总是被提升为双精度(就像在varargs中将char和short提升为int一样)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|191689|将float看作是一种简约的double可能比把double看作一种扩展的float更好。也就是说，double是首选的浮点类型，在某些特定情况下，只要需要较小版本的double，就会使用float。这是我所知道的最接近连贯的原因，然后规则是有意义的，即使你碰巧需要一个较小的版本。|offset|length|style|CODE|191690|entityMap^0|0|1|5|E|6|O|6|11|5|1E|6|2B|6|2M|5|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]|$D|N|E|O|F|G]|$D|P|E|Q|F|G]|$D|R|E|S|F|G]|$D|T|E|U|F|G]|$D|V|E|W|F|G]|$D|X|E|Y|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|I|$]]

C and C++ prefer double to float in a couple of ways. As you noticed, fractional literals are double unless explicitly made floats. Also, floats can't be passed in varargs, they're always promoted to double (in the same way char and short are promoted to int in varargs).

It's probably better to think of <code>float</code> as being a contracted <code>double</code>, rather than <code>double</code> being an extended <code>float</code>. That is, <code>double</code> is the preferred floating point type, and <code>float</code> is used whenever a smaller version of <code>double</code> is required for some particular case. That's the closest I know to a coherent reason, and then the rule makes sense, even if you happen to be in the case where you need a smaller version.

blocks|key|3856273|text|这不是MSVC独有的，这是语言标准所要求的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3856274|我建议，除非明确要求，否则不降低精度是有意义的，因此默认值是双精度。|3856275|单精度浮点数提供的6位有效精度很少足以用于一般用途，而且在现代桌面处理器上肯定会用作手工编码的优化，因为写入者已经确定这是足够和必要的；因此，需要一个显式的可视标记来指定单精度文字是有意义的。|3856276|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

This is not peculiar to MSVC, it is required by the language standard.

I would suggest that it made sense not to reduce precision unless explicitly requested, so the default is double. 

The 6 significant digits of precision that a single-precision float provides is seldom sufficient for general use and certainly on a modern desktop processor would be used as a hand coded optimisation where the writer has determined that it is sufficient and necessary; so it makes sense that an explicit visible marker is required to specify a single-precision literal.

blocks|key|191866|text|也许是因为double比float好得多，接近3.14？以下是确切的值：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|191867|3.140000000000000124344978758017532527446746826171875+(double)|191868|3.1400001049041748046875+(float)|191869|entityMap^0|5|6|C|5|0|1J|6|0|Q|5|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@$9|U|A|V|B|C]]|D|@]|E|$]]|$1|J|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|K|$]]

Because <code>double</code> can approximate 3.14 much better than <code>float</code>, maybe? Here are the exact values:

3.140000000000000124344978758017532527446746826171875 (<code>double</code>)

3.1400001049041748046875 (<code>float</code>)

Why do I need to put 3.14f instead of 3.14 to disable all those warnings ?
Is there a coherent reason reason for this ?

Why floating point value such as 3.14 are considered as double by default in MSVC?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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为什么我需要使用3.14f而不是3.14来禁用所有这些警告？这是不是有一个连贯的原因？

问为什么像3.14这样的浮点值在MSVC中默认为双精度？
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问为什么像3.14这样的浮点值在MSVC中默认为双精度？EN