いや、マジでなるんですけど…。

D:\study\haskell>type aa.hs
mytake 0 _ = []
mytake n (x:xs) = x: take (n-1) xs

D:\study\haskell>ghci aa.hs
　　　___ ___ _
　　/ _ \ /\ /\/ __(_)
　/ /_\// /_/ / / | | GHC Interactive, version 6.4.2, for Haskell 98.
/ /_\\/ __ / /___| | http://www.haskell.org/ghc/
\____/\/ /_/\____/|_| Type :? for help.

Loading package base-1.0 ... linking ... done.
Compiling Main ( aa.hs, interpreted )
Ok, modules loaded: Main.
*Main> mytake 10 [1,2]
[1,2]
*Main> mytake (-1) [1,2]
[1]
*Main>