Re: [Haskell-cafe] Access to list

On 13 Jan 2008, frr149@easyjob.net wrote:

If I define the follwoing functions:

car (x:_) = x car [] = []

This won't typecheck. It helps to add a type signature car :: [a] -> a The first element of an empty list is undefined, so you can do what Prelude.head does and write: car [] = undefined

cdr (_:xs) = xs cdr [] = []

This is entirely valid, but may not be what you want. cdr [] = undefined -- like Prelude.tail Jed