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Q: Haskell question ( No Answer,   1 Comment )
Question  
Subject: Haskell question
Category: Computers > Programming
Asked by: exitmusic_-ga
List Price: $15.00
Posted: 19 Apr 2005 05:13 PDT
Expires: 19 May 2005 05:13 PDT
Question ID: 511271
I want to know an elegant way to convert from coordinates (any amount
of dimensions) using a list of lists, to coordinates using a list of
tuples (eg pairs).  I'm using Floats.

for example, 3 points in 2 dimensions from [[1,2],[4,5],[7,8]]  to 
[(1,2),(4,5),(7,8)]

or 2 points in 3 dimensions from [[1,2,3],[4,5,6]]  to [(1,2,3),(4,5,6)]

So the function type would probably be  [[Float]] -> [(Float)]

Thanks
Answer  
There is no answer at this time.

Comments  
Subject: Re: Haskell question
From: dmpots-ga on 22 Apr 2005 03:26 PDT
 
I think that the function you want may be impossible.  The problem is
that there is no type that is a tuple of arbitrary length. This makes
it impossible to define the function you want.

Check out the "Gentle Introduction to Haskell"
(http://www.haskell.org/tutorial/goodies.html) for more details. In
particular the section describing tuples states:
---
At this point the reader should note carefully the differences between
tuples and lists, which the above definitions make abundantly clear.
In particular, note the recursive nature of the list type whose
elements are homogeneous and of arbitrary length, and the
non-recursive nature of a (particular) tuple type whose elements are
heterogeneous and of fixed length.
---

You could rather easily define a function that could take a list of
lists into a tuple of fixed size.

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