On Nov 16, 12:36 am, samppi <[EMAIL PROTECTED]> wrote:
> Is there a way to get a value—call it 'anything—so that (isa? anything
> x) is always true for any x?
>
> I need this for multimethod dispatch—sometimes, I want a method to
> ignore some of the stuff its dispatch function returns:
>
> (defmulti a #(%1 %2))
>
> (defmethod a [3 2] [x y] ...)
>
> ; in this method, the second dispatch value is ignored and
> ; the method matches any call whose first argument is 5
>
> (defmethod a [5 anything] [x y] ...)
>
> I wish the _ symbol would do this, but it doesn't work (if practical,
> it'd be cool if it were implemented in the future :). Is there some
> sort of solution possible right now?
There could be some problem constraints I don't understand
here but maybe you could just use "first" (or some custom
function) to extract the relevant args
user=> (defmulti a #(first [%1 %2]))
#'user/a
user=> (defmethod a 3 [x y] :three)
#<MultiFn [EMAIL PROTECTED]>
user=> (defmethod a 5 [x y] :five)
#<MultiFn [EMAIL PROTECTED]>
user=> (a 3 4)
:three
user=> (a 3 5)
:three
user=> (a 5 5)
:five
Parth
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