为什么求幂从右到左? [英] Why is exponentiation applied right to left?

问题描述

我正在阅读Python入门教材，并碰到了这一行:

I am reading an Intro to Python textbook and came across this line:

同一行上的运算符具有相同的优先级，并从左到右应用，除幂运算(从右到左应用).

Operators on the same row have equal precedence and are applied left to right, except for exponentiation, which is applied right to left.

我了解大多数情况，但我不明白为什么他们说从右到左应用了幂运算.他们也没有提供任何示例.另外，我可以问这样的一般性问题吗，还是只喜欢解决问题的问题?

I understand most of this, but I do not understand why they say exponentiation is applied right to left. They do not provide any examples either. Also, am I allowed to ask general questions like this, or are only problem solving questions preferred?

推荐答案

**运算符遵循

The ** operator follows normal mathematical conventions; it is right-associative:

在通常的计算机科学术语中，数学中的幂是右相关的，这意味着x ^{y z} 应该读作x ^{(y z )}，而不是(x ^y ) ^z .在对BODMAS规则的阐述足够谨慎以解决此问题时，规则是首先评估最高指数.

In the usual computer science jargon, exponentiation in mathematics is right-associative, which means that x^yz should be read as x^(yz), not (x^y)^z. In expositions of the BODMAS rules that are careful enough to address this question, the rule is to evaluate the top exponent first.

，并来自有关操作顺序 的维基百科:

and from Wikipedia on the Order of Operations:

如果幂用堆叠符号表示，则通常的规则是从上向下进行计算，因为幂在数学上是右联想的.

If exponentiation is indicated by stacked symbols, the usual rule is to work from the top down, because exponention is right-associative in mathematics.

所以2 ** 3 ** 4的计算方式是2 ** (3 ** 4)(== 2417851639229258349412352)，而不是(2 ** 3) ** 4(== 4096).

So 2 ** 3 ** 4 is calculated as 2 ** (3 ** 4) (== 2417851639229258349412352) not (2 ** 3) ** 4 (== 4096).

这在编程语言中非常普遍；尽管有 例外，但它被称为 right-associativity (右关联).

This is pretty universal across programming languages; it is called right-associativity, although there are exceptions, with Excel and MATLAB being the most notable.

这篇关于为什么求幂从右到左?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！