Re: Power function as operator

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