[Haskell-beginners] A simple function V2

[Ezequiel Hernan Di Giorgi]

First i want to thank all the persons who responded me yesterday to help
me. Thanks! I am so happy with with your friendliness.
So i have other beginners question:

Now i want a improved version of my* intercalate*. Now i want to call a
function with two [t][t] and obtain another one which have only
even elements, even because:

   - [1,2,3,3,4][6] and the ouput [1,6]
   - [1,2,3,4][5,6,7] output [1,5,2,6,3,7]

I tried it:

*intercalate :: (Eq t) => [t] -> [t] -> [t]*
*intercalate (x:xs) (y:ys)*
* | xt == [] = []*
* | yt == [] = []*
* | otherwise = x : y : intercalate xs ys*
* where xt=(x:xs)*
*            yt=(y:ys)*

but i get nice error

**Main> intercalate [1][6]*
*[1,6*** Exception: baby.hs:(2,1)-(5,51): Non-exhaustive patterns in
function intercalate*
*
*
**Main> *

(yes...the file's name is baby.hs)

Thanks in advance! (: (: (:
(: (:
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