[Haskell-cafe] How to construct a lazy list of eagerly-evaluated items?

[Vladimir Ch.]

> Not really. Your problem is that you calculate maxPaths vals over and over
> again in
>   where mpath i val = val + maximum [(maxPaths vals) !! pi| pi <- prev i]
> ; the value isn't shared (it is, if compiled with optimisations).
> If you share the list by giving it a name, your programme becomes much
> faster (interpreted or compiled without optimisations; with -O, it's below
> measuring accuracy anyway) and needs only a little memory:
>
> maxPaths vals@(v:vs) = mps
>  where
>    mps = v : zipWith mpath [1 .. ] vs
>    mpath i val = val + maximum [mps !! pi| pi <- prev i]
>

Thank you - exactly the kind of answer I was looking for!