So does this mean that the reason for complexity of generics is the Java inheritance?
BTW, in addition to the article I posted, This site: http://www.angelikalanger.com/GenericsFAQ/JavaGenericsFAQ.html has a FAQ on Java generics that is 500+ pages long! In Haskell you have parametrized types but I don't think you need 500+ page faq to explain it. daryoush On Thu, Oct 16, 2008 at 12:27 PM, Jonathan Cast <[EMAIL PROTECTED]>wrote: > On Thu, 2008-10-16 at 12:27 -0700, Robert Greayer wrote: > > --- On Thu, 10/16/08, Jonathan Cast <[EMAIL PROTECTED]> wrote: > > > So if I say > > > > > > void wrong(List<?> foo, List<?> bar) > > > > > > I get two /different/ type variables implicitly filled in? > > > > > > If I declare a generic class, and then have a method, is > > > there a way, in > > > that method's parameter list, to say `the type > > > parameter that was > > > supplied when my class was instantiated'? > > > > > > > Yes - > > class Foo<T> { > > ... > > void right(List<T> foo, List<T> bar) { > > foo.add(bar.get(0)); > > } > > > > Can also do it at the method level... > > > > void <T> alsoRight(List<T> foo, List<T> bar) { ... } > > > > > Yikes. So, in this instance, the difference between > > > Haskell and Java > > > is: if you want to disallow that call to wrong, in Haskell > > > you can... > > > > > > > Not exactly... Java disallows 'wrong' from being written (without > > class casts and such), because it disallows calling a method which has > > a wildcard type in a contravariant position. IIRC, Scala handles all > > this more elegantly. If you stay away from '?', and stick to type > > variables with Java generics, though, how type checking with generics > > works in Java should be mostly unsurprising to a Haskeller. > > Oh, good. > > Daryoush Mehrtash: > > It looks like the answer to your original question --- gotchas with Java > generics vs. Haskell polymorphism --- is that the `gotchas' you linked > to are consequent on using ? in your code, instead of true type > variables. So the truly problematic construct is ?, and the difference > is just that Haskell doesn't have an analogue to it. > > jcc > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
