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#!/usr/bin/env guile
!#
(use-modules (ice-9 rdelim)
(srfi srfi-1)
(srfi srfi-60))
(define (bit-frequency acc)
(let* ((num-string (read-line))
(num-length (string-length num-string))
(num (string->number num-string 2)))
(if (integer? num)
(let* ((num-freq-list (map (lambda (b) (if b '(1 0) '(0 1))) ;; 101 -> 5 -> '(#t #f #t) -> '((1 0) (0 1) (1 0))
(integer->list num num-length)))
(next-acc (if (null? acc) ;; If we have not yet accumulated anything
num-freq-list ;; Return the current value as the new accumulator.
;; Otherwise add each pair to the previous accumulator.
(map (lambda (xs ys) (map + xs ys))
acc num-freq-list))))
(bit-frequency next-acc))
acc))) ;; If the input was not an integer (ie EOF) return what we have accumulated.
;; Capture the result of bit-frequency in a closure.
(define bit-frequency-to-num
(let ((bf (bit-frequency '())))
;; The closure applies a predicate to the frequency of 1s and 0s seen for the current bit.
;; If the predicate returns true, the current bit is 1, and vice versa.
(lambda (predicate)
(list->integer
(map (lambda (freq) (apply predicate freq))
bf)))))
(define gamma-rate (bit-frequency-to-num >)) ;; Gamma rate is the number with the most common bits.
(define epsilon-rate (bit-frequency-to-num <)) ;; Epsilon rate is the number with the least common bits.
(define power-consumption (* gamma-rate epsilon-rate)) ;; Power consumption is the gamma rate * the epsilon rate.
(display power-consumption)
(newline)
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