elm-lazy

This library provides a way of putting of computations until they are needed, allowing for expensive calculations later.

lazySum : Lazy Int
lazySum =
    lazy (\() -> sum <| List.range 1 1000000)

It also gives you a way of storing a computed value so that you do not need to re-compute it.

lazySum : Int -> Lazy Int
lazySum n =
    lazy (\() -> sum <| List.range 0 n)


lazySums : List Int -> List (Lazy Int)
lazySums sums =
    List.map lazySum sums

-- evaluates the head, before putting it back on the list
evaluteCurrentSum : List (Lazy Int) -> List (Lazy Int)
evaluteCurrentSum xs =
   case xs of 
     head::rest -> Lazy.evaluate head :: rest
     _ -> []

Notes

This is a library based originally on the old Lazy implementation. However, it is written entirely in pure Elm. The main difference is explicit memoization, as we no longer use side-effects to achieve laziness.