Andrew Coppin wrote:
Bulat Ziganshin wrote:
people that make critique on haskell type classes, don't take into
account that it's unlike C++ templates, implemented via run-time
dictionaries and other modules may define new instances
Personally, I have no clue how C++ templates work [yet]. (As in, I'm
learning C++, but I haven't got to that chapter yet.)
Some guy told me that templates are "the best feature in the language",
and proceeded to show me a huge chunk of highly complex-looking code
which is approximately equivilent to
join :: Array x -> Array x -> Array x
I was unimpressed.
Actually, that's a lie. I was impressed that such a low-level language
could manage even that much abstraction. But I still prefer the Haskell
way...
C++ values have sizes:
class foo {
int x;
};
is half (ahem; make that "different from") the size of
class bar {
int x;
int y;
};
As a result, doing parametric polymorphism requires duct taping
something suspiciously similar to cpp macros to the type system. Hence,
how C++ templates work: weirdly.
Java (and presumably C#) "generics" are very much like a weakened
version of normal parametric polymorphism. C++ templates are an attempt
at the same thing in a completely different landscape. I'd be willing
to bet that Some Guy's code was very close to exactly equivalent to your
join.
Now, as to what C++ templates have to do with Haskell type classes, I
dunno...
--
Tommy M. McGuire
[EMAIL PROTECTED]
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