On Feb 26, 8:30 am, Laurent PETIT <laurent.pe...@gmail.com> wrote:
> 2009/2/26 Rich Hickey <richhic...@gmail.com>
>
>
>
>
>
> > On Feb 26, 4:17 am, Laurent PETIT <laurent.pe...@gmail.com> wrote:
> > > 2009/2/26 Konrad Hinsen <konrad.hin...@laposte.net>
>
> > > > On 26.02.2009, at 01:51, Rich Hickey wrote:
>
> > > > > You raise interesting issues and I'd like to explore them further.
> > I'm
> > > > > not sure the issues you have with type-tag-or-class dispatch are all
> > > > > that prohibitive. In any case, I've added a type function that
> > returns
> > > > > the :type metadata or the class if none:
>
> > > > Thanks, that helps a lot! With a built-in universal dispatching
> > > > function, most of my problems should be solved. Another useful
> > > > function to have would be
>
> > > > (defn type-instance?
> > > > "Evaluates x and tests if it is an instance of the type or class t.
> > > > Returns true or false"
> > > > [t x]
> > > > (identical? t (type x)))
>
> > > > for type-based dispatching inside a function.
>
> > > or maybe generalize the existing 'instance? function to the above
> > definition
> > > ?
>
> > I'm not sure I'd want to do that. You'd still need actual class
> > detectors.
>
> But the definition and implementation of the above 'type-instance? function
> works for classes, and I don't think the point of the current instance? is
> to check that the given class parameter is a real class or not ? It is
> checking the type of the instance passed to it ?
>
> Or am I missing something ?
>
The definition above is definitely broken in using identical?
I'll think about extending instance? to use type + isa?
Rich
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