what is parse error: naked expression at top level?

Question

I was trying to get the length of each element, given a nested list; and I also I want to get rid of the repeated length.

For example, a nested list [[1],[1,2],[4..5]] should give me [1,2].

I can do it in the interactive by nub (map length [[1],[1,2],[4..5]]). But if I write a file with the following code:

Import Data.List
getLen :: [[a]] ->[Int]
getLen xs = nub (map length xs)

I got the error saying:

"Parse error: naked expression at top level"

What does this error mean and how can I fix this?

Answer 1

Simple change: it's import not Import.