Nice distinction! Thank you for the correction. Il giorno 02/nov/2010, alle ore 09.11, Roel van Dijk

ha scritto:

On Mon, Nov 1, 2010 at 7:23 PM, uu1101@gmail.com wrote:

...

* _ is not a special keyword in haskell. It's a regular variable so will always match. It's usually used when you don't use it's value in the right hand side or when it adds no information. In this case its value will be n so there is no reason to introduce another name.

This is incorrect. _ is a pattern not a variable.

I can write

f (_:_) = "bla"

but not

f (x:x) = "bla" Conflicting definitions for `x' In the definition of `f'

So _ is a pattern that always matches but is never bound to a value.

Regards, Roel