[Haskell-beginners] How memorize intermediate computation value[my brain is so hurt]?
David McBride
toad3k at gmail.com
Sat Feb 4 12:12:57 CET 2012
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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