[Haskell-cafe] Pattern matching on numbers?
ryani.spam at gmail.com
Tue Nov 18 18:44:04 EST 2008
How does this work?
> fac n = case n of
> 0 -> 1
> _ -> n * fac (n-1)
ghci> :t fac
fac :: (Num t) => t -> t
The first line of "fac" pattern matches on 0. So how does this work
over any value of the Num typeclass? I know that the "1" on the rhs
of fac are replaced with (fromInteger 1), but what about numeric
literals in patterns? Does it turn into a call to (==)?
Should whatever technique is used be extended to other typeclasses too?
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