[Haskell-cafe] Newb question about map and a list of lists

Jules Bean jules at jellybean.co.uk
Fri Sep 28 16:47:04 EDT 2007

Chuk Goodin wrote:
> I have a list of lists of pairs of numeric Strings (like this: 
> [["2","3"],["1","2"],["13","14"]] etc.) I'd like to change it into a 
> list of a list of numbers, but I'm not sure how to go about it. If it 
> was just one list, I could use map, but map.map doesn't seem to work. 
> Any suggestions, or pointers to a reference online?

Your instinct to use map.map is correct.

Just be careful to write:

(map.map) read l


map.map $ read l

beware that:

map.map read l

is parsed as map.(map read l)...


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