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Permutations with repetitions: Difference between revisions

Permutations with repetitions (view source)

Revision as of 09:40, 22 September 2018

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→‎Applescript lazy evaluation: pruned a redundant function, edited a sub-title
(→‎Applescript lazy evaluation: pruned a redundant function, edited a sub-title)
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<lang AppleScript>{{1, 1}, {1, 2}, {1, 3}, {2, 1}, {2, 2}, {2, 3}, {3, 1}, {3, 2}, {3, 3}}</lang>
 
===PartialLazy evaluation with a generator===
Permutations with repetition by treating the <math>n^k</math> elements as an ordered set, and writing a function from a zero-based index to the nth permutation. This allows us terminate a repeated generation on some condition, or explore a sub-set without needing to generate the whole set:
<lang AppleScript>use AppleScript version "2.4"
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return out & dbl
end replicate
 
-- take :: Int -> [a] -> [a]
-- take :: Int -> String -> String
on take(n, xs)
set c to class of xs
if list is c then
if 0 < n then
items 1 thru min(n, length of xs) of xs
else
{}
end if
else if string is c then
if 0 < n then
text 1 thru min(n, length of xs) of xs
else
""
end if
else if script is c then
set ys to {}
repeat with i from 1 to n
set end of ys to xs's |λ|()
end repeat
return ys
else
missing value
end if
end take
 
-- toLower :: String -> String
Hout
9,659

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