[Haskell-beginners] How memorize intermediate computation value[my brain is so hurt]?

[David McBride]

There are quite a few packages on hackage that do memoization.  Many
of them actually have fibonacci sequences as examples.  These vary in
terms of complexity.

http://hackage.haskell.org/package/data-memocombinators
http://hackage.haskell.org/package/monad-memo
http://hackage.haskell.org/package/memoize



On Sat, Feb 4, 2012 at 5:36 AM, anyzhen <jiangzhen3s at qq.com> wrote:
> there have a lot of situation we need memorize intermediate computation
> value.
> and use in further.
> like this, compute nth fib question.
> So,how memorize it?
>
> i have an ugly solution.it used HashTable for memorization.
>
> fib n table
>  | n==1 =1
>  | n==2 =1
>  | otherwise =
>   case lookup table of
>     Just v   ->(v,table)
>     Nothing ->let (v,table') = fib (n-1) table in
>                    let ( v',table'')= v + fib(n-2) table' in
>                    (v',table'')
>
> i am an beginner come from imperative programming language.
> so fib memorize version program hurt my brain ... particular in Nothing
> branches.
> so do you have some good idea
>
>
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