Hi !
An interresting point of clojure is that it is dynamically typed. This
for a reason. There is a tradeoff in performance but the benefit is
that the code is shorter, more expressive and reusable.
Type hinting should be exceptionnal and used only in critical areas
when you see a huge boost in performance. And if you need this boost.
I think then that's the library author responsability and own right to
figure by himself where ultimate performance is needed or instead
where greater flexibility is to be prefered.
Bye,
Nicolas.
On Nov 21, 5:12 pm, Tassilo Horn <tass...@member.fsf.org> wrote:
> Herwig Hochleitner <hhochleit...@gmail.com> writes:
>
> Hi Herwig,
>
> > In principle you're right. But you have to keep in mind, that type
> > hints actually alter runtime behavior.
>
> > A hinted call tries to cast its argument into the desired type,
> > possibly resulting in a type cast exception. An unhinted call, on the
> > other hand, just looks for the signature.
>
> > So in essence a hinted call can fail for cases where an unhinted call
> > succeeds, effectively reducing composability at a type level
> > (polymorphism).
>
> Hm, indeed. This function works for any java object that has a
> zero-parameters doubleValue() method.
>
> (defn double-val [x] (.doubleValue x))
>
> In contrast,
>
> (defn double-val [x] (.doubleValue ^Integer x))
>
> will fail for (double-val 7), because by default any integer is a Long
> in Clojure 1.3. However, one could go with
>
> (defn double-val [x] (.doubleValue ^Number x))
>
> instead, and that works fine for Integer, Long, Double, ... But of
> course, it's not applicable for
>
> class Foo { String doubleValue() {return "foo";} }
>
> whereas the non-type-hinted version is. Note that this doubleValue()
> method doesn't even return a double.
>
> But is that really an issue? I mean, since you cannot use such duck
> typing in Java itself (except in terms of reflection), any method
> defined for more than one class with shared, consistent semantics is
> declared in some common parent class or interface which you can use for
> your type hint.
>
> Bye,
> Tassilo
> --
> (What the world needs (I think) is not
> (a Lisp (with fewer parentheses))
> but (an English (with more.)))
> Brian Hayes,http://tinyurl.com/3y9l2kf
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