Re: [Haskell-cafe] Why isn't pattern matching lazy by default?

f ~(x:xs) = x + 2 f ~[] = 42

Then f [] would give a complie error: Irrefutable pattern failed for pattern (x : xs)

Sorry, that should be *runtime* error! Chris.

Hope that gives some insight. Chris.

...

Oh well, the way it is now is also easy to get used to, one just has to know how it works (just like M-theory ;-) )

Cheers, Peter

Neil Mitchell wrote:

...

Hi

...

...

Now why isn't pattern matching lazy by default? This seems odd for a newbie since everything else is lazy by default.

f ~(x:xs) = rhs f ~[] = rhs'

Now guess what f [] does...

If you use a where binding then pattern matching is lazy.

Thanks

Neil

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe