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Simplify List.walk (e.g. for dev backend)

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Richard Feldman 2023-08-15 02:15:56 -04:00
parent 6c8b1963ae
commit bac445b39b
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1 changed files with 12 additions and 3 deletions
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15
crates/compiler/builtins/roc/List.roc
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@ -459,9 +459,18 @@ contains = \list, needle ->
## Note that in other languages, `walk` is sometimes called `reduce`,
## `fold`, `foldLeft`, or `foldl`.
walk : List elem, state, (state, elem -> state) -> state
walk = \list, state, func ->
walkHelp : _, _ -> [Continue _, Break []]
walkHelp = \currentState, element -> Continue (func currentState element)
walk = \list, init, func ->
walkHelp list init func 0 (List.len list)
## internal helper
walkHelp : List elem, s, (s, elem -> s), Nat, Nat -> s
walkHelp = \list, state, f, index, length ->
if index < length then
nextState = f state (List.getUnsafe list index)
walkHelp list nextState f (Num.addWrap index 1) length
else
state
when List.iterate list state walkHelp is
Continue newState -> newState