计算负数的幂 [英] Calculate power of a negative number

问题描述

我对C#相对较新，由于Math.Pow(x，y)返回负数的NaN(读:不是负幂)，所以我想知道如何更有效地计算结果.我现在正在写的内容是一个基本的for循环，但是我想知道它是否可以以更短的方式实现(也许使用Linq)?

I relatively new to C# and since Math.Pow(x,y) returns NaN for a negative number(read: not negative power), I want to know how to calculate result more efficiently. What I am doing write now is a basic for loop, but I want to know if it can be implemented in shorter way (using Linq maybe)?

for(int i=0;i<power;i++)
       {
           result = result * num;
       }

推荐答案

Math.Pow(x,y)返回NaN为负数.

那是因为没有为负数基定义任意幂:

That's because arbitrary exponentiation is not defined for a negative base:

http://en.wikipedia.org/wiki/Exponentiation

当基数b为正实数时，可以通过指数函数为所有实数甚至复数指数n定义b到n的值

when the base b is a positive real number, b to the n can be defined for all real and even complex exponents n via the exponential function

现在，如果幂是整数(如您的情况)，则定义了负数的幂以得到真实的结果，但是Pow不会为您计算它.您应该做的是:

Now, exponentiation of negative numbers to get a real result is defined if the power is an integer, as in your case, but Pow will not calculate it for you. What you should do is:

• 假设您想了解Pow(-2, 5)
• 改为Pow问题Pow(2, 5).
• 看看指数；如果它是偶数，那么您将得到正确的答案.如果它是一个奇数，则答案是否定的.

• Suppose you want to know Pow(-2, 5)
• Give Pow the problem Pow(2, 5) instead.
• Look at the exponent; if it is an even number then you've got the right answer. If it is an odd number, then make the answer negative.

因此，在这种情况下，Pow(2, 5)返回32.指数5为奇数，因此将其设为-32，就可以了.

So in this case, Pow(2, 5) returns 32. The exponent 5 is odd, so make it -32, and you're done.

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