Re: Unifying logical operators

On 11 July 2018 at 03:20, Ryan <iggyvolz@gmail.com> wrote: > > PHP 7 code should never be blindly upgraded to PHP 8 (which is what this > would target for actual changes, not just deprecation/notices). This would > have to be clearly stated in the upgrade guide. > There's a big difference between "not blindly updating" and "having to run a static analysis tool and carefully read its results to stop your code having a subtly different behaviour". Introducing new errors is nearly always better than silently changing behaviour (this is the entire principle of run-time type checks, after all). > On Tue, Jul 10, 2018 at 5:01 AM, Rowan Collins <rowan.collins@gmail.com> > wrote: > > As your own next example demonstrates, it does rely on the difference in > > precedence, because without it, you could only use this idiom after > > carefully checking that the left-hand side would be evaluated in one go, > > and probably using an extra set of parentheses. > > > > The defined or die idiom does not depend on precedence, because it doesn't > contain an assignment operator. One could theoretically do > $isDefined=defined("X") or die() - however that would be pointless as > $isDefined would always be true. > Right, which is why I said your *next* example, which did use assignment. The point is that *reliably using the idiom* requires a specific precedence, so that you don't have to carefully vet which other operators are involved in the expression. > > While I've not seen it used much in PHP code, the "do this or die" idiom > > is common in Perl (which also has post-fix "if" and "unless" > > modifiers, > so > > those are a different feature again). > > > > Forgive my lack of knowledge with perl, but it looks[1] like they only > support a postfix if and postfix unless operators - which can serve the > same purpose as PHP's and/or (x and y => y if x, x or y => y unless !x). > Perhaps I worded that badly. I was saying two things: - The "do or die" idiom is extremely common in Perl. Just searching the documentation should be enough to convince you of that: https://duckduckgo.com/?q=site%3Aperldoc.perl.org+"or+die" - Perl *also* has post-fix if and unless operators, which you had mentioned in Ruby (Ruby inherited a lot from Perl). Clearly, people don't see these as a better replacement for the use of "or". > My thought for aliasing is that it may help with legacy code (if you're not > relying on the return value, which is 99% of cases), as well as there being > no symbolic equivalent for xor (as you state below it's not equivalent to > != as I thought) > Just to reiterate, I strongly feel that aliasing is not an option. If the aim is to reduce confusion, having the same code give different results in different PHP versions is a massive own goal. > On Tue, Jul 10, 2018 at 2:37 PM, Kalle Sommer Nielsen <kalle@php.net> > wrote: > > > > > I personally wanted to extend this syntax but I never got around to it > > to support: "do() or throw new Exception(...);", tho its just a code > > style over: "if(!do()){ throw new Exception(...); }" > > > > do() or throw doesn't actually work because throw is a language construct, > not a function. > Yes, hence "wanted to extend this syntax" - the suggestion is that this would be a useful feature to add, not one that already exists. > > A more readable syntax, if we were designing from scratch, might be to > > look at SmallTalk, where ifTrue and ifFalse are methods on the boolean > > class, so can appear post-fix after any boolean, giving you something > like: > > > > $connected ifFalse: die(); > > > > I hesitate to propose adding a new syntax to PHP, especially for something > so rarely used it makes me question if it's truly necessary. If anything I > would think we should prefer a syntax that we can point to other languages > as examples (like the if/unless syntax from Ruby). It feels odd to clean > up a rarely used operator by replacing it with fresh syntactical sugar. > I agree that adding new syntax is unnecessary for this, but since you keep mentioning the postfix if/unless which Ruby inherited from Perl, I thought I'd point to another language we could borrow syntax from, which is actually closer to the current idiom ("condition keyword action", not "action keyword condition"). Regards, -- Rowan Collins [IMSoP]