Type classes vs C++ overloading Re: [Haskell-cafe] Messing around
with types [newbie]
cristiano.paris.ml at gmail.com
Fri Jun 22 05:56:40 EDT 2007
On 6/22/07, Tomasz Zielonka <tomasz.zielonka at gmail.com> wrote:
> The problem is not that it can't tell whether 5.0 and 10 would fit Int
> and Double (actually, they do fit), it's that it can't tell if they
> won't fit another instance of FooOp.
You expressed the concept in more correct terms but I intended the same...
I'm starting to understand now.
> Instances are duplicate if they have the same (or overlapping) instance
> heads. An instance head is the thing after =>. What's before => doesn't
So, the context is irrelevant to distinguishing instances?
> It seems that Num and Fractional are somewhat related. Any hint?
> It's not important here, but indeed they are:
> class (Num a) => Fractional a where
I see. Thank you Tomasz.
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