112 lines
2.0 KiB
AppleScript
112 lines
2.0 KiB
AppleScript
-- UNION AND DIFFERENCE
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-- union :: [a] -> [a] -> [a]
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on union(xs, ys)
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nub(xs & ys)
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end union
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-- difference :: [a] -> [a] -> [a]
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on difference(xs, ys)
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script except
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on lambda(a, y)
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if a contains y then
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|delete|(y, a)
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else
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a
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end if
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end lambda
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end script
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foldl(except, xs, ys)
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end difference
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-- TEST
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on run
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set a to ["John", "Serena", "Bob", "Mary", "Serena"]
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set b to ["Jim", "Mary", "John", "Jim", "Bob"]
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-- 'Symmetric difference'
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union(difference(a, b), difference(b, a))
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--> {"Serena", "Jim"}
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end run
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-- GENERIC LIBRARY 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 lambda(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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-- unique set of members of xs
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-- nub :: [a] -> [a]
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on nub(xs)
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if (length of xs) > 1 then
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set x to item 1 of xs
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[x] & nub(|delete|(x, items 2 thru -1 of xs))
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else
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xs
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end if
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end nub
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-- uncons :: [a] -> Maybe (a, [a])
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on uncons(xs)
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if length of xs > 0 then
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{item 1 of xs, rest of xs}
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else
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missing value
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end if
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end uncons
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-- deleteBy :: (a -> a -> Bool) -> a -> [a] -> [a]
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on deleteBy(fnEq, x, xs)
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if length of xs > 0 then
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set {h, t} to uncons(xs)
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if lambda(x, h) of mReturn(fnEq) then
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t
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else
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{h} & deleteBy(fnEq, x, t)
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end if
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else
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{}
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end if
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end deleteBy
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-- delete :: a -> [a] -> [a]
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on |delete|(x, xs)
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script Eq
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on lambda(a, b)
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a = b
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end lambda
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end script
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deleteBy(Eq, x, xs)
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end |delete|
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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 lambda : f
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end script
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end if
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end mReturn
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