It looks like the matchure <http://github.com/dcolthorp/matchure.git> does
this kind of thing .. :) .. I guess somebody has already written a library
to do what I wanted ...
On Mon, Sep 6, 2010 at 9:44 AM, Sunil S Nandihalli <
sunil.nandiha...@gmail.com> wrote:
> Hi Mark,
> Let us say my dispatch function always returns a vector of 4 keywords. now
> I want to write my methods in the following way..
>
> (defmethod foo [_ :hello _ _ ] (str "I'm method 1"))
> (defmethod foo [:world _ :us _ ] (str "I'm method 2"))
> (defmethod foo [:city _ :us _ ] (str "I'm method 3"))
>
> and so on ..
>
> where '_' would match with anything ...
>
> but I just realized I could probably create a type of my own which
> overrides the default '=' operator and make it behave like this .. do you
> think that would work?
>
> Sunil.
>
>
>
> On Mon, Sep 6, 2010 at 9:36 AM, Mark Rathwell <mark.rathw...@gmail.com>wrote:
>
>>
>> Sorry, little slow today. I'm not sure I'm completely following what you
>> are trying to achieve. What do you want your method prototypes to look
>> like? (e.g. modify the below to be what you are envisioning):
>>
>> (defmulti foo mclass)
>> (defmethod foo "1" [s] (str "I'm method 1"))
>> (defmethod foo "2" [s] (str "I'm method 2"))
>>
>>
>>
>> On Sun, Sep 5, 2010 at 11:58 PM, Sunil S Nandihalli <
>> sunil.nandiha...@gmail.com> wrote:
>>
>>> Thanks Mark for you reply. Well I realized we can do that .. but I feel
>>> it would be more expressive and readable if I could do the wild-card like
>>> pattern matching when I am defining the method.
>>> Sunil.
>>>
>>>
>>> On Mon, Sep 6, 2010 at 9:25 AM, Mark Rathwell
>>> <mark.rathw...@gmail.com>wrote:
>>>
>>>>
>>>> You can add essentially one more level of indirection to your dispatch
>>>> function logic and return an integer (or string or whatever) and match on
>>>> that. So, with your example, when you want "method1" called, return 1 from
>>>> the dispatch function, when you want "method2" return 2, you get the idea:
>>>>
>>>> (defmulti foo mclass)
>>>> (defmethod foo 1 [s] (str "I'm method 1"))
>>>> (defmethod foo 2 [s] (str "I'm method 2"))
>>>> ...
>>>>
>>>> Is this what you are getting at?
>>>>
>>>> - Mark
>>>>
>>>> On Sun, Sep 5, 2010 at 8:50 PM, Sunil S Nandihalli <
>>>> sunil.nandiha...@gmail.com> wrote:
>>>>
>>>>> Hello everybody,
>>>>> It is awesome that we can specify our own dispatch functions and
>>>>> corresponding values.. However, I feel we should also have control over
>>>>> the
>>>>> functions that is used to match the value of the dispatch function with
>>>>> that
>>>>> of the one specified in the defmethod.
>>>>> For instance if my dispatch function is
>>>>>
>>>>> *(defn mclass [s]*
>>>>> * (vec (reverse (loop [ret '() val s]*
>>>>> * (if (coll? val)*
>>>>> * (recur (cons (class val) ret) (first val))*
>>>>> * (cons (class val) ret))))))*
>>>>>
>>>>> which basically tries to give a list of all the nested types of a
>>>>> value. If a value is a collection, then all its elements are of same type.
>>>>> so the above function when applied on .. let us say
>>>>>
>>>>> *(mclass #{'([1 2] [3 4])*
>>>>> * '([5 6] [7 8])})*
>>>>>
>>>>> the return value would be
>>>>>
>>>>> *[clojure.lang.PersistentHashSet clojure.lang.PersistentList
>>>>> clojure.lang.PersistentVector java.lang.Integer]*
>>>>>
>>>>> I would like to despatch based on some pattern of the return value of
>>>>> my dispatch function *mclass*
>>>>> *
>>>>> *
>>>>> For instance I would like to say something like when the second element
>>>>> of return value of the dispatch function is *PersistentList call
>>>>> method1 and call method2 when say the first element is PersistentList and
>>>>> second element is say PersistentHashSet and call method3 for some
>>>>> other pattern. Basically a general pattern matching .. So if only I could
>>>>> have a way of changing how the equality for the purpose of dispatching
>>>>> behaves .. it would be wonderful. We could either do this or we could
>>>>> change
>>>>> the dispatch-val to a dispatch-function with a single argument .. Or is
>>>>> there a way to already do this?*
>>>>>
>>>>> In short is it possible to do a generic pattern-matching during
>>>>> dispatch in multimethods?
>>>>>
>>>>> Sunil.
>>>>>
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>>>>
>>>>
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>>>
>>>
>>>
>>
>
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