From: "Martin J. Dürst" <duerst@...>
Date: 2012-10-27T06:25:31+09:00
Subject: [ruby-core:48359] Re: [ruby-trunk - Feature #6678] Precedence of ^ operator

On 2012/10/27 1:04, trans (Thomas Sawyer) wrote:
>
> Issue #6678 has been updated by trans (Thomas Sawyer).
>
>
> I take it you read the article? Do you see the issue I am having in need of an operator with a precedence above + - * and /? So what solution would you recommend?

http://trans.github.com/2009/12/13/a-failure-of-precedence.html gives me 
a 404 (There isn't a GitHub Page hosted here, sorry.).

https://github.com/trans/trans.github.com/wiki/2009-12-13-a-failure-of-precedence 
works, and I have read it. There's just one single example/use case. It 
seems inappropriate to claim that this is a big problem with just a 
single example/use case.

Also, what about alternatives such as 2.square.meters, or 2.meters.squared ?

Also, you say: "On the other hand, some simple issues doggedly persist 
for little good reason (backward compatibility not withstanding).". This 
sounds to me as if you think that backwards compatibility wasn't a 
problem at all. But who is going to fix all these scripts out there that 
rely on the current precedence?


> Note, I am not saying '^' should stop being XOR, or that it should become power operator for Numeric. I just was asking if it could get a higher precedence, so it could be used for such in custom classes. As a broader question, why are the bitwise operators lower in precedence that math operators? Is there are reason for that (other then that's how everyone has always done it). I've read that even Dennis Ritchie admits that the precedence of operators in C, which everyone has copied, isn't optimal.

This is third-hand knowledge, and not in any way specific to "^", or the 
absence of other operators with the same precedence as "**" (because C 
doesn't have that). Also, I don't think Dennis Ritchie would agree 
changing operator precedences in a widely used programming language. 
(unfortunately, we can't ask him anymore)

Regards,    Martin.

> ----------------------------------------
> Feature #6678: Precedence of ^ operator
> https://bugs.ruby-lang.org/issues/6678#change-31614
>
> Author: trans (Thomas Sawyer)
> Status: Rejected
> Priority: Normal
> Assignee:
> Category: core
> Target version: Next Major
>
>
> I wrote about this here: http://trans.github.com/2009/12/13/a-failure-of-precedence.html (or https://github.com/trans/trans.github.com/wiki/2009-12-13-a-failure-of-precedence if you prefer)
>
> In short I would like to see `^` operator move up in precedence to be the same as `**`. We need another option besides `**` at the top of precedence list and `^` fits the bill well since many languages already think of it as "power of".
>
> Of course, this has downside that effects current use for XOR definition. A new operator would be needed for that but `^` could alias it by default, so only thing that changes is precedence. Thankfully XOR is not among the most commonly used operators and often when used the precedence will be okay either way. So there should be very few cases where new operator or parenthesis will need to be put in.
>
> Ultimately it would be great if precedence could be controlled on per-class basis. But that is big change, and might not be altogether practical. So I propose this one modest adjustment instead in which it would be an improvement.
>
>
>