Lets say I've got
Interface IFoo<X,Y>
Where X : IBar
Where Y : IBar
{
}
Would seem to translate roughly to....
class (IBar x, IBar y) => IFoo foo x y
? (or does it?)
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Nicholls, Mark
Sent: 28 December 2007 11:30
To: Chaddaï Fouché
Cc: haskell-cafe@haskell.org
Subject: RE: [Haskell-cafe] what does @ mean?.....
Lovely....thank you very much....another small step forward.
-----Original Message-----
From: Chaddaï Fouché [mailto:[EMAIL PROTECTED]
Sent: 28 December 2007 11:29
To: Nicholls, Mark
Cc: Alfonso Acosta; haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] what does @ mean?.....
2007/12/28, Nicholls, Mark <[EMAIL PROTECTED]>:
> So in the example given...
>
> mulNat a b
> | a <= b = mulNat' a b b
> | otherwise = mulNat' b a a
> where
> mulNat' x@(S a) y orig
> | x == one = y
> | otherwise = mulNat' a (addNat orig y) orig
>
> Is equivalent to
>
> mulNat a b
> | a <= b = mulNat' a b b
> | otherwise = mulNat' b a a
> where
> mulNat' (S a) y orig
> | (S a) == one = y
> | otherwise = mulNat' a (addNat orig y) orig
>
> ?
Yes, but in the second version, it has to reconstruct (S a) before
comparing it to "one" where in the first it could do the comparison
directly. In this cas there may be some optimisation involved that
negate this difference but in many case it can do a real performance
difference.
The "as-pattern" (@ means as) is both practical and performant in most cases.
--
Jedaï
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