Re: [RFC] Callable Types

On Sat, 23 Apr 2016 14:18:56 +0300, Dan Ackroyd <danack@basereality.com> wrote:

On 22 April 2016 at 05:12, Marcio Almada <marcio.web2@gmail.com> wrote:

Hello everyone, We just completed the draft for the "Callable Types" RFC.

There seems to be one thing missing from the RFC; please could you add an example where the parameter and return types are also 'typed' callables? Presumably it would look something like this? function reduce(int $a, int $b, callable(int, callable(int, int):int $math):int $reducer): callable(int, int):int { return $reducer($a, $b); } Are there any limits to how far down the callable type can be defined ? cheers Dan

Hey Dan, thanks for reviewing. I have just added a paragraph about nested callables, I'll copy paste it here: Nested callables can be used with no imposed limit on the nesting level.

    function foo(callable(callable(int)) $cb) {
        $cb(function (int $i) {
            var_dump($i);
        });
    }

    foo(function (callable(int) $intPrinter) {
        $intPrinter(123);
    });

There's currently no way to reference callable signature from within itself, meaning there's no way to make recursive signatures like below:

    function bar(callable(int $number): callable(int $number): callable(int $number): parent_callable $recursiveCb) { // this wouldn't work currently
    }

To add to that, nested callables can get pretty unreadable quickly, both of these problems would be best solved by a typedef feature of some kind, added to PHP later.