[Haskell-beginners] Error while using indices and elem

Chaddaï Fouché chaddai.fouche at gmail.com
Mon Apr 21 09:26:34 UTC 2014

On Mon, Apr 21, 2014 at 10:06 AM, Nishant <nishantgeek at gmail.com> wrote:

> Hi,
> Do I need to define indices and elem for Graph a w here explicitly ?
> import Data.Array
> data Graph a w = Array a [(a,w)]
> -- array (1,3) [(1,[(2,3),(3,2)])]
You probably meant to make "Graph a w" a type synonym but you used "data"
thus it is a type constructor with one data constructor named Array which
takes two parameters : an "a" and a list of pairs of "a" and "w".
You wanted to write :

> type Graph a w = Array a [(a,w)]

which should work better (indices will work on it like on an Array from

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