Re: First-class callable partial application

On Tue, 14 Mar 2023 at 10:39, Bob Weinand <bobwei9@hotmail.com> wrote: > Hey Rowan, > > do we actually need *positional* partial application, after a ... token? > > Would it not be enough, to simply forbid positional arguments after a ... > and just allow named arguments? These already have well defined position > independent semantics. > > There may be some desire for a single argument placeholder later on, but > this can be introduced later, separately. > Yes, named parameters would certainly be better than left-to-right only. It's definitely less elegant, though, and given that PFA is largely short-hand for a short closure anyway, I think conciseness is quite an important aim. To take a couple of the above examples, and compare existing short closure, fully positional PFA, and named-after-placeholder PFA: $isLogger = fn($object) => is_subclass_of($object, LoggerInterface::class, false); $isLogger = is_subclass_of(?, LoggerInterface::class, false); $isLogger = is_subclass_of(..., class: LoggerInterface::class, allow_string: false); $priceFormatter = fn(float $num) => number_format($num, 2, ',', '.'); $priceFormatter = number_format(?, 2, ',', '.'); $priceFormatter = number_format(..., decimals: 2, decimal_separator: ',', thousands_separator: '.'); Arguably the named param version is more explicit, but in some cases it's significantly longer than manually defining a closure, whereas fully positional PFA is always shorter. Regards, -- Rowan Tommins [IMSoP]