You could probably make it work in cljs by:
1. Putting IMultiMethod back to cljs version, except using is-a?, not
core/isa?
2. Rewrite the Is-A protocol code to use the cljs rules:
- Remove any code about class hierarchies
- Only extend Is-A on actual types, so cljs.core.Vector, not
IPersistentVector, cljs.core.ObjMap, not IPersistentMap
Of course, I have maybe 2 days total of cljs experience, so an expert can
jump on this thread any time :) .
Re: #2 above, is what I'm doing in my JVM clojure code (extending on
IPersistentVector, etc.) considered bad form? I ask because:
- from http://clojure.org/protocols : "You can implement a protocol on
an interface... opens the door to incidental multiple inheritance of
implementation... which [interface] is used is unspecified." When I read
that, I thought "Oh, lord. I'm going to have a horrible C++ nightmare
tonight."
- But I've seen extension on interfaces in basically all of the JVM
clojure.core.* code. Are they using some undocumented convention so that
the above problem won't happen?
Also, does someone know of a good example of testing code that modifies
global state? Right now I'm adding multimethods and derive-ing things,
extending protocols, etc.. I'd like to make sure tests don't interfere
with each other.
This might all be off topic. Should I start a new thread (or two)?
--Leif
On Saturday, July 14, 2012 4:44:37 AM UTC-4, Dave Sann wrote:
>
> Can this be used in clojurescript?
>
> It looks like yes
>
> But, taking the given clj example, my first question is how can I extend a
> protocol to the equivalent of IPersistentMap. Given that maps in
> clojurescript are protocols, this seems harder.
>
> D
>
>
> On Wednesday, 11 July 2012 16:52:47 UTC+10, Leif wrote:
>>
>> Thanks!
>>
>> The similarity is no accident: When you consider it, 'isa?' is a
>> generalized subtyping relation:
>>
>> (isa? Double Number) ==> Double <: Number
>> (isa? ::goat ::animal) ==> ::goat <: ::animal
>> (isa? 1 x) ==> #{1} <: x, which makes sense if you define the value x to
>> mean "the set of all things equivalent to x"
>>
>> Specifically for the keyword case, clojure.core lets you define ad hoc
>> hierarchies, which you could view as type lattices. This project lets you
>> define ad hoc type lattice relations.
>>
>> You might be interested in the papers on LIFE. They define "sorts" for
>> logic terms (very much like types), and an algorithm for unifying two terms
>> (which can be quite a bit more complicated than Prolog terms).
>>
>> On Wednesday, July 11, 2012 2:22:51 AM UTC-4, Ambrose Bonnaire-Sergeant
>> wrote:
>>>
>>> This is cool :)
>>>
>>> It reminds me of subtyping between maps in Typed Clojure, where
>>>
>>> {:a 1, :b 2} <: {:a Number}
>>>
>>> Thanks,
>>> Ambrose
>>>
>>> On Wed, Jul 11, 2012 at 2:16 PM, Leif <leif.poor...@gmail.com> wrote:
>>>
>>>> Hi, everybody. I reimplemented the function isa? in terms of a
>>>> protocol Is-A.
>>>>
>>>> The reason why you would want to do that is in the README at
>>>> https://github.com/leifp/clj-isa-protocol
>>>>
>>>> tl;dr: One of the reasons why people are excited about predicate
>>>> dispatch is the irritation caused by the dispatch function of a
>>>> multimethod
>>>> being closed. You have to decide up front what information the dispatch
>>>> fn
>>>> is going to pull out of your arguments. Changing it afterward is a pain.
>>>>
>>>> Since the dispatch uses 'isa?' internally, if that function is
>>>> extensible, then multimethod dispatch becomes, to a certain extent, open.
>>>> See the README.
>>>>
>>>> Comments, critique, code, and questions welcome.
>>>>
>>>> Cheers,
>>>> Leif
>>>>
>>>> P.S. As an aside to people that like weird, obscure programming
>>>> languages, the rough idea of how is-a? should work for maps was inspired
>>>> by
>>>> (but very much simpler than) the functional logic language LIFE [
>>>> http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.90.3175 ]
>>>>
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>>>
>>>
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