179 lines
3.8 KiB
AppleScript
179 lines
3.8 KiB
AppleScript
-- equilibriumIndices :: [Int] -> [Int]
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on equilibriumIndices(xs)
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script balancedPair
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on |λ|(a, pair, i)
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set {x, y} to pair
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if x = y then
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{i - 1} & a
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else
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a
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end if
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end |λ|
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end script
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script plus
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on |λ|(a, b)
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a + b
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end |λ|
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end script
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-- Fold over zipped pairs of sums from left
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-- and sums from right
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foldr(balancedPair, {}, ¬
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zip(scanl1(plus, xs), scanr1(plus, xs)))
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end equilibriumIndices
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-- TEST -----------------------------------------------------------------------
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on run
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map(equilibriumIndices, {¬
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{-7, 1, 5, 2, -4, 3, 0}, ¬
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{2, 4, 6}, ¬
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{2, 9, 2}, ¬
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{1, -1, 1, -1, 1, -1, 1}, ¬
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{1}, ¬
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{}})
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--> {{3, 6}, {}, {1}, {0, 1, 2, 3, 4, 5, 6}, {0}, {}}
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end run
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-- GENERIC FUNCTIONS ----------------------------------------------------------
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-- foldl :: (a -> b -> a) -> a -> [b] -> a
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on foldl(f, startValue, xs)
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tell mReturn(f)
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set v to startValue
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set lng to length of xs
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repeat with i from 1 to lng
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set v to |λ|(v, item i of xs, i, xs)
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end repeat
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return v
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end tell
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end foldl
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-- foldr :: (a -> b -> a) -> a -> [b] -> a
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on foldr(f, startValue, xs)
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tell mReturn(f)
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set v to startValue
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set lng to length of xs
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repeat with i from lng to 1 by -1
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set v to |λ|(v, item i of xs, i, xs)
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end repeat
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return v
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end tell
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end foldr
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-- init :: [a] -> [a]
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on init(xs)
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set lng to length of xs
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if lng > 1 then
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items 1 thru -2 of xs
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else if lng > 0 then
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{}
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else
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missing value
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end if
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end init
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-- map :: (a -> b) -> [a] -> [b]
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on map(f, xs)
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tell mReturn(f)
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set lng to length of xs
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set lst to {}
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repeat with i from 1 to lng
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set end of lst to |λ|(item i of xs, i, xs)
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end repeat
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return lst
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end tell
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end map
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-- min :: Ord a => a -> a -> a
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on min(x, y)
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if y < x then
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y
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else
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x
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end if
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end min
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-- Lift 2nd class handler function into 1st class script wrapper
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-- mReturn :: Handler -> Script
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on mReturn(f)
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if class of f is script then
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f
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else
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script
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property |λ| : f
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end script
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end if
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end mReturn
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-- scanl :: (b -> a -> b) -> b -> [a] -> [b]
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on scanl(f, startValue, xs)
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tell mReturn(f)
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set v to startValue
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set lng to length of xs
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set lst to {startValue}
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repeat with i from 1 to lng
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set v to |λ|(v, item i of xs, i, xs)
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set end of lst to v
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end repeat
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return lst
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end tell
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end scanl
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-- scanl1 :: (a -> a -> a) -> [a] -> [a]
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on scanl1(f, xs)
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if length of xs > 0 then
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scanl(f, item 1 of xs, tail(xs))
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else
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{}
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end if
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end scanl1
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-- scanr :: (b -> a -> b) -> b -> [a] -> [b]
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on scanr(f, startValue, xs)
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tell mReturn(f)
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set v to startValue
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set lng to length of xs
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set lst to {startValue}
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repeat with i from lng to 1 by -1
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set v to |λ|(v, item i of xs, i, xs)
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set end of lst to v
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end repeat
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return reverse of lst
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end tell
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end scanr
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-- scanr1 :: (a -> a -> a) -> [a] -> [a]
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on scanr1(f, xs)
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if length of xs > 0 then
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scanr(f, item -1 of xs, init(xs))
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else
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{}
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end if
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end scanr1
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-- tail :: [a] -> [a]
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on tail(xs)
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if length of xs > 1 then
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items 2 thru -1 of xs
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else
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{}
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end if
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end tail
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-- zip :: [a] -> [b] -> [(a, b)]
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on zip(xs, ys)
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set lng to min(length of xs, length of ys)
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set lst to {}
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repeat with i from 1 to lng
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set end of lst to {item i of xs, item i of ys}
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end repeat
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return lst
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end zip
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