CODEWITHSUNDEEP
syntaxhaskell
Andariel
Andariel

Reputation: 133

Haskell- Pattern syntax in expression context: _

I have been learning some Haskell and writing very simple programs. I want to make a function that will return the element at the given position. Here's what I tried to do-

elempos::Int->[a]->a
elempos n (b:_)=head (drop n (b:_) )

But I'm getting this error when I load the Test.hs file in the GHCi editor. 

Pattern syntax in expression context: _

And it says Failed, modules loaded:none. Since I'm very new to the language I don't really have a proper idea what the mistake is(currently at chapter 4 of learn you a haskell). Can anyone tell me what is wrong here?

Upvotes: 5

Views: 7638

Answers (1)

Cat Plus Plus
Cat Plus Plus

Reputation: 129814

_ is valid only inside patterns, you're trying to use it inside an expression: head (drop n (b : _)). Since you don't really need to decompose the list, and you do need the tail, the solution is to do:

elempos n xs = head (drop n xs)

Upvotes: 11

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