[Haskell-cafe] Re: data structures question

[Tamas K Papp]

On Thu, Aug 31, 2006 at 11:09:07AM +0400, Bulat Ziganshin wrote:
> Hello Benjamin,
> 
> Wednesday, August 30, 2006, 11:40:09 PM, you wrote:
> 
> > Matthias Fischmann wrote:
> >> The trick is that Int is not the only index data type, but tuples of
> >> index data types are, too.  Do this:
> >> 
> >> | type Point = (State, State, Int)
> >> | type TypeV = Array State Double
> >> | 
> >> | matrix :: TypeV
> >> | matrix = array bounds values
> >> |    where
> >> |    ...
> 
> > Surely you meant to say
> 
> > | type TypeV = Array Point Double
> 
> which will require 128 gigs of memory for 32-bit cpus and even
> slightly more for 64-bit ones :)

Bulat,

Can you please explain this?  The following code works fine for me,
and I don't have that much RAM ;-) It seems I am not getting
something.


import Data.Array

data State = Low | High deriving (Eq,Ord,Ix,Show)

other :: State -> State
other High = Low
other Low = High

type Point = (State,State,Int)
type TypeV = Array Point Double

f (Low,Low,a) = a

matrix = array ((Low,Low,0),(Low,Low,4)) [(i,f(i)) | i <- range ((Low,Low,0),(Low,Low,4))]


Thank you,

Tamas