Haskell newtype Tuple Constructor

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Haskell

Hi guys,

I'm somewhat new to Haskell and I'm stuck with the following.

I have this type:

newtype Node = N (String,[Edge])
newtype Graph = G([Node])
n2s (N (n,e)) = n

How come I can't use:

n2s :: Node -> String
n2s n = fst n

If n is a tuple then you should be able to do this right?

Whenever I do this I get the following error:

Couldn't match expected type '<string,b0>' with actual type 'Node'.

Any ideas?

Also the following doesn't work. Same error:

edges (G([])) = []
edges (G(n:ns)) = snd n ++ edges (G(ns))

Thanks in advance