Re: Power function as operator

On Fri, Nov 22, 2013 at 6:37 PM, Nikita Popov <nikita.ppv@gmail.com> wrote: > On Fri, Nov 22, 2013 at 5:58 PM, Tjerk Meesters <tjerk.meesters@gmail.com > >wrote: > > > Hi, > > > > To challenge myself I had tasked myself to introduce a new operator and > > opcode to the language; now that I'm done with it, I wanted to measure > the > > response on the list to actually get it merged before writing an RFC. > > > > My work can be found here: > > https://github.com/datibbaw/php-src/compare/pow-operator > > > > It introduces the pow() function as an operator ** (double asterisk), as > > can be found in languages such as Python (with perhaps the notable > > difference that it's right associative there). > > > > The logic gets exposed via the ZEND_POW opcode and all the logic that > went > > into pow() itself is copied into it. The exceptions are that an > expression > > such as [] ** 2 (squared empty array) will cause a fatal error because > the > > operands are incompatible, whereas pow([], 2) would give 0. > > > > Why this operator? Basically because: > > 1) it's shorter (the keyboard rejoices). > > 2) it's faster (no ZEND_CALL). > > 3) it's found in other languages too. > > > > I've only implemented one of the test suites; there are quite a few for > > just one function, but when needed I can add those others as well. > > > > Btw, changes to vld aren't pushed yet. > > > > Let me know! > > > > I don't really see a need for this operator in PHP. From my experience > pow() isn't some particularly commonly used function, so I don't think it > needs its own operator. (But I don't think that adding it would > particularly hurt either...) > > Anyway, if this is added I would strongly recommend to make the operator > non-associative. I have no idea how Python came up with the idea to make ** > right-associative, which violates basic programming language design rules > (all binary non-assignment operators are left-associative) and goes against > (at least my) common sense, but now that they made the choice it's likely > unwise to deviate from it by making it left-associative in PHP (see ternary > operator mess...) So I think making it non-associative makes for a safe > middle ground. This will cause 2 ** 3 ** 2 to throw an error and require > you to group it as either (2 ** 3) ** 2 or 2 ** (3 ** 3). Less ambiguity. > > Nikita > I'm not entirely sure that making it non-associative is a great idea either, but I have to agree that it does find *some* middle ground. Right-associative exponent operator didn't seem right to me either.