Entropy: Difference between revisions
→{{header|Haskell}}: Added a variant, expressed in terms of an applicative.
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(→{{header|Haskell}}: Added a variant, expressed in terms of an applicative.) |
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where lg c = -c * logBase 2 c
fq c = let sc = sum c in map (/ sc) c</lang>
Or, inlining with an applicative expression (turns out to be fractionally faster):
<lang haskell>import Data.List (genericLength, group, sort)
entropy
:: (Ord a, Floating c)
=> [a] -> c
entropy =
sum .
map (negate . ((*) <*> logBase 2)) .
(map =<< flip (/) . sum) . map genericLength . group . sort
main :: IO ()
main = print $ entropy "1223334444"</lang>
{{out}}
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