[Haskell-cafe] Java - Haskell adjustment

Jules Bean jules at jellybean.co.uk
Mon Oct 15 11:09:09 EDT 2007

Ryan Bloor wrote:
> Hi, its Ryan here...
> I've just come from an intensive course in java and have been thrown 
> into the imperative world of haskell.
> The problem that I have is extremely simple in java but I am having 
> trouble adjusting my old mindset.
> A multiset is a collection of items.
> Each item may occur one or more times in the multiset. All items are of 
> the same type.
> The scenario we could use is a students' grades for their A levels: 3A, 
> 4B and 2C grades for our pupil 'x'.
> A multiset may be implemented by a list... so ['A', 'A', 'A', 'B', 'B', 
> 'B', 'B, 'C', 'C'] but this very ineffiecient and tedious.
> How might one set out into putting this into action.... thanks...

Why do you think a list is inefficient and tedious? It sounds fine for 
this simple application.

If you have complexity constraints which rule a list out, then consider 
Data.Sequence. Actually Data.Sequence has a very similar API to the 
programmer; you will feel much like you're using List, but it is faster 
for certain things. (most things, in fact).


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