[Haskell-cafe] ghc has problems with 'zipWith' ?
ddarius at hotpop.com
Wed Dec 8 08:17:49 EST 2004
> Is it possible and senseful for a compiler to extract common
> sub-expressions? Naively I think that for a given tree of an
> expression it is efficiently possible to find all common sub-trees.
> Referential transparency would assure that equal expressions have the
> same value, so they can be replaced by the same object. E.g. the
> example above could be automatically transformed to:
> ms as =
> let tmp0 = zipWith (+) (zipWith (*) as tmp1) (0:tmp1)
> tmp1 = 1:tmp0
> in tmp0
It's possible and will preserve semantics, but isn't always an
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