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