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Fix iterateBackwards

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Richard Feldman 2022-07-22 10:45:38 -04:00 • committed by Folkert
parent 1c2047fbeb
commit d60ad6b5af
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1 changed files with 12 additions and 18 deletions
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30
crates/compiler/builtins/roc/List.roc
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@ -795,14 +795,14 @@ findFirst = \list, pred ->
## Returns the last element of the list satisfying a predicate function. ## Returns the last element of the list satisfying a predicate function.
## If no satisfying element is found, an `Err NotFound` is returned. ## If no satisfying element is found, an `Err NotFound` is returned.
findLast : List elem, (elem -> Bool) -> Result elem [NotFound]* findLast : List elem, (elem -> Bool) -> Result elem [NotFound]*
findLast = \array, pred -> findLast = \list, pred ->
callback = \_, elem -> callback = \_, elem ->
if pred elem then if pred elem then
Break elem Break elem
else else
Continue {} Continue {}
when iterateBackwards array {} callback is when List.iterateBackwards list {} callback is
Continue {} -> Err NotFound Continue {} -> Err NotFound
Break found -> Ok found Break found -> Ok found
@ -825,12 +825,12 @@ findFirstIndex = \list, matcher ->
## satisfying a predicate function can be found. ## satisfying a predicate function can be found.
## If no satisfying element is found, an `Err NotFound` is returned. ## If no satisfying element is found, an `Err NotFound` is returned.
findLastIndex : List elem, (elem -> Bool) -> Result Nat [NotFound]* findLastIndex : List elem, (elem -> Bool) -> Result Nat [NotFound]*
findLastIndex = \list, matcher -> findLastIndex = \list, matches ->
foundIndex = iterateBackwards list (List.len list - 1) \index, elem -> foundIndex = List.iterateBackwards list (List.len list) \prevIndex, elem ->
if matcher elem then if matches elem then
Break index Break (prevIndex - 1)
else else
Continue (index - 1) Continue (prevIndex - 1)
when foundIndex is when foundIndex is
Break index -> Ok index Break index -> Ok index
@ -981,11 +981,8 @@ iterHelp : List elem, s, (s, elem -> [Continue s, Break b]), Nat, Nat -> [Contin
iterHelp = \list, state, f, index, length -> iterHelp = \list, state, f, index, length ->
if index < length then if index < length then
when f state (List.getUnsafe list index) is when f state (List.getUnsafe list index) is
Continue nextState -> Continue nextState -> iterHelp list nextState f (index + 1) length
iterHelp list nextState f (index + 1) length Break b -> Break b
Break b ->
Break b
else else
Continue state Continue state
@ -996,17 +993,14 @@ iterateBackwards = \list, init, func ->
iterBackwardsHelp list init func (List.len list) iterBackwardsHelp list init func (List.len list)
## internal helper ## internal helper
iterBackwardsHelp : List elem, s, (s, elem -> [Continue s, Break b]), Nat, Nat -> [Continue s, Break b] iterBackwardsHelp : List elem, s, (s, elem -> [Continue s, Break b]), Nat -> [Continue s, Break b]
iterBackwardsHelp = \list, state, f, prevIndex -> iterBackwardsHelp = \list, state, f, prevIndex ->
if prevIndex > 0 then if prevIndex > 0 then
index = prevIndex - 1 index = prevIndex - 1
when f state (List.getUnsafe list index) is when f state (List.getUnsafe list index) is
Continue nextState -> Continue nextState -> iterBackwardsHelp list nextState f index
iterHelp list nextState f index Break b -> Break b
Break b ->
Break b
else else
Continue state Continue state