9 lines
344 B
Common Lisp
9 lines
344 B
Common Lisp
(defun entropy (string)
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(let ((table (make-hash-table :test 'equal))
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(entropy 0))
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(mapc (lambda (c) (setf (gethash c table) (+ (gethash c table 0) 1)))
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(coerce string 'list))
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(maphash (lambda (k v) (decf entropy (* (/ v (length input-string)) (log (/ v (length input-string)) 2))))
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table)
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entropy))
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