Re: Type hinting - Request for Discussion

2009/7/10 Alain Williams <addw@phcomp.co.uk> > On Fri, Jul 10, 2009 at 01:35:45PM +0300, Ionut G. Stan wrote: > > On 7/10/2009 13:23, Giovanni Giacobbi wrote: > > >On Fri, Jul 10, 2009 at 02:44:52AM +0200, troels knak-nielsen wrote: > > >[...] > > > > > >>For example, instead of: > > >> > > >> function addFive(int $x) { > > >> return $x + 5; > > >> } > > >> > > >>You would simply do: > > >> > > >> function addFive(is_numeric $x) { > > >> return $x + 5; > > >> } > > >> > > >>Since $x is guaranteed to be numeric, it is safe to to arithmetic on > > >>it. No reason to explicitly type cast here. > > >> > > >> > > I like it too. Not only it solves the initial problem, but it also > > allows userland extensions. For example, > > the current patch does not provide checks for callables, but we already > > have is_callable in the core. > > Hmmm, but it makes simple cases more complicated and slower. But I do like > the > idea of generalising it with a function to handle 'strange' cases. > > So, we have 3 syntaxes: > > 1) function Foo(int $x) { > > $x is tested to be integer, if it isn't an error is raised - either by > exception > or just a fatal error. > > A problem with this is that it could yeild some surprising results, eg: > > Foo(4/2); -- OK > Foo(4/3); -- FAIL since 4/3 yeilds a float > > In this last case people would learn to: > > Foo((int)(4/3)); > > > 2) function Foo((int) $x) { > > $x is cast to int, ie converted iff possible - otherwise an error is > raised: > int -> int -- OK > float -> int -- OK if in the range for integer > string -> int -- OK iff it is 100% clean: > '10' - OK > '10.1' - OK as string -> float -> int > '10ten' - FAIL/ERROR > etc > > What happens when someone tries to use this syntax where he is casting to > an object ? > I suggest that this fails unless the object has a __cast method, in which > case that is invoked: > > function Foo((MyObject) $x) { > ... > } > > class MyObject { > function __cast($x) { > if( ..... ) > return new Foo('abcd', $x); > .... > } > ... > } > > > 3) function Foo(is_int($x)) { > > Function is_int is called, an error is raised if it returns false. > But then you're complicating it to the point where it's no longer much more useful than just calling the is_numeric method in the function body. Plus there's no longer the advantage of optimisers knowing the data-type. Lewis.