C++中的指数运算符
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Exponential Operator in C++
提问by James Hayek
I am taking a class in C++ and I noticed there are only a few math operators to use. I also noticed that C++ does not come with an exponential operator within its math library.
我正在上 C++ 课程，我注意到只有几个数学运算符可以使用。我还注意到 C++ 的数学库中没有指数运算符。
Why must one always write a function for this? Is there a reason for the makers of C++ to omit this operator?
为什么必须始终为此编写一个函数？C++ 的制造者是否有理由省略这个运算符？
回答by paxdiablo
You don'twrite a function for this (unless you're insane, of course). There's a perfectly good powfunctiondefined in the <cmath>header.
您不会为此编写函数（当然，除非您疯了）。标题中定义了一个非常好的pow函数<cmath>。
Aside:if you try to use
^as a power operator, as some people are wont to do, you'll be in for a nasty surprise. It's the exclusive-or (XOR) operator (see here).
旁白：如果您尝试
^用作电力运营商，正如某些人习惯做的那样，您会遇到令人讨厌的惊喜。它是异或 (XOR) 运算符（请参阅此处）。
回答by msw
Most C operations readily intended tomapped to a single processor instruction when C was invented. At the time, exponentiation was not a machine instruction, thus the library routine.
大多数C操作容易意图映射到单个处理器指令当C被发明。当时，取幂不是机器指令，因此是库例程。
回答by PixelsTech
According to Bjarne Stroustrup in his book The design and evolution of C++. They decided to avoid exponential operator because :
根据 Bjarne Stroustrup 在他的书C++ 的设计和演变中的说法。他们决定避免使用指数运算符，因为：
- An operator provides notational convenience, but does not provide any new functionality. Members of the working group, representing heavy users of scientific/engineering computation, indicated that the operator syntax provides minor syntactic convenience.
- Every user of C++ must learn this new feature
- Users have stressed the importance of susbtituting their own specialized exponentiation functions for the system default, which would not be possible with an intrinsic operator
- The proposal is not sufficiently well motivated. In particular, by looking at one 30000 line Fortran program one cannot conclude that the operator would be widely used in C++
- The proposal requires adding a new operator and adding another precedence level thus increasing the complexity of the language
- 运算符提供符号方便，但不提供任何新功能。代表科学/工程计算重度用户的工作组成员表示，运算符语法提供了次要的语法便利。
- 每个 C++ 用户都必须学习这个新功能
- 用户强调了将他们自己专门的求幂函数替换为系统默认值的重要性，这对于内部运算符是不可能的
- 该提案的动机不够充分。特别是，通过查看一个 30000 行的 Fortran 程序，您无法得出该运算符将在 C++ 中广泛使用的结论
- 该提案需要添加一个新的运算符并添加另一个优先级，从而增加了语言的复杂性
回答by Manoj R
What platform and which compiler are you using? My guess is TurboC. Mostly cmath file has most of the mathematical functions covered in other compilers.
您使用的是什么平台和编译器？我的猜测是 TurboC。大多数 cmath 文件具有其他编译器中涵盖的大多数数学函数。
