Exponentiation operator precedence

Claude Pache claude.pache at gmail.com
Thu Sep 24 18:08:29 UTC 2015


> Le 24 sept. 2015 à 16:11, Brendan Eich <brendan at mozilla.org> a écrit :
> 
> And indeed apart from dot (a special form whose right operand must be a lexical identifier-name) and square brackets (which isn't an infix operator per se), unary operators bind tighter than binary in JS as in C and other C-derived languages.

I just wonder why it is important that unary binds tighter? For instance, before I carefully studied the issue of this thread, I have never expected that unary minus binds tighter than binary multiplication operator in expressions like `-2*x` (although it does not matter in that case).

> 
> without having to parenthesize unduly, but one cannot write
> 
> let z = -x ** y;
> 
> The user is forced by an early error to write either (-x)**y or -(x**y).

In traditional math notation, when you mean `(-x)**n`, you write (-x)ⁿ with mandatory parentheses, so I don’t expect that many people will be tempted to miswrite it `-x ** n`.

Making the parentheses mandatory here will be somewhat annoying in perfectly reasonable expressions, where you usually don’t use parentheses in real math notation., like:
```
let s2 =  - x**2 - y**2 - z**2 +  t**2
```

—Claude


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