[Haskell-cafe] Problems interpreting

[Andrea Rossato]

On Mon, Sep 18, 2006 at 12:54:34PM +0200, Albert Crespi wrote:
> Thank you very much for your reply!
> As I said, it is my first experience with Haskell, I have been programming
> in Java and C for some years, and I find this language very different from
> them. Anyway I'll try to fix the function with the information that you gave
> me.
> Thanks again!
> 
You're welcome.

By the way, this is what the comments say you are trying to do:

-- Replaces a wildcard in a list with the list given as the third argument
substitute :: Eq a => a -> [a] -> [a] -> [a]
substitute e l1 l2= [c | c <- check_elem l1]
    where check_elem [] = l1
          check_elem (x:xs) = if x == e then (l2 ++ xs) else check_elem xs

This is the result:

*Main> substitute 1 [1,2,3] []
[2,3]
*Main> substitute 1 [1,2,3] [7,8,9]
[7,8,9,2,3]
*Main>     

Have fun with Haskell.

Ciao
Andrea