当我包含< limits>时，有什么区别?或< limits.h>在我的C ++代码中 [英] What difference does it make when I include <limits> or <limits.h> in my c++ code

问题描述

有人可以解释一下吗?

    #include <iostream>
    #include <limits.h>

或

    #include <iostream>
    #include <limits>

推荐答案

<limits> 是C ++标准库标头提供与C标头<limits.h>类似的见解(在C ++中也可以作为 <climits> )，但是它的编写方式在C ++程序中更加有用和安全:

<limits> is a C++ Standard Library header providing similar insights to the C header <limits.h> (which is also available in C++ as <climits>), but it is written in a way that's more useful and safe in C++ programs:

• 假设您有一个template <typename Numeric> ...，并且内部代码想知道用户实例化模板所使用的Numeric类型参数的最小值和最大值:您可以使用std::numeric_limits<Numeric>::min()和;如果要从<climits>访问相同的值，则很难知道要使用SCHAR_MIN，SHRT_MIN，INT_MIN，LONG_MIN等中的哪个，并且必须在它们之间进行切换所有人-如此琐碎的事情有很多额外的代码

• say you have a template <typename Numeric> ..., and the code inside wants to know the minimum and maximum value of the Numeric type parameter that the user instantiated your template with: you can use std::numeric_limits<Numeric>::min() and ...::max(); if you wanted to access the same values from <climits>, it'd be hard to know which of SCHAR_MIN, SHRT_MIN, INT_MIN, LONG_MIN etc. to use and you'd have to switch between them all yourself - lots of extra code for something so trivial

<climits>有很多宏，并且宏不像常规" C ++标识符那样尊重名称空间或范围-它们的替换非常随意-因此它们使您的程序更容易出错

<climits> has lots of macros, and macros don't respect namespaces or scopes the way "normal" C++ identifiers do - their substitutions are made pretty indescriminately - so they make your program more error prone

<limits>提供了有关数字类型的更多信息，例如它们是否带符号，它们可以处理的以10为基数的数字，是否可以表示无穷大或无数字的定点值等. .(有关完整列表和信息，请参见标题文档)

<limits> gives much more insight about numeric types, such as whether they're signed, the number of base-10 digits they can handle, whether they can represent infinity or not-a-number sentinel values etc. (see the header docs for a fuller list and information)

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