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#!/usr/bin/guile -s
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!#
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(use-modules (ice-9 rdelim))
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(define (read-lines)
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(let loop ((line (read-line)))
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(if
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(eof-object? line)
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'()
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(cons line (loop (read-line))))))
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(define (map list mapper)
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(if
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(null? list)
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'()
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(cons (mapper (car list)) (map (cdr list) mapper))))
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(define (reduce list reducer current)
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(if
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(null? list)
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current
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(reduce (cdr list) reducer (reducer current (car list)))))
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(define (combine a b combiner)
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(if (null? a) b (if (null? b) a (combiner a b))))
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(define (sum numbers) (reduce numbers + 0))
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(define
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(repeat value number)
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(if
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(= number 0)
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'()
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(cons value (repeat value (- number 1)))))
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(define (is-numeric-char char) (if (char-numeric? char) #t #f))
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(define (first-last list predicate)
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(reduce
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(map list (lambda (entry)
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(if (predicate entry) (repeat entry 2) '())))
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(lambda (current accumulator)
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(combine
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current
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accumulator
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(lambda (current rest) (cons (car current) (cdr rest)))))
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'()))
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(define (solve-line line)
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((lambda (first-last-result)
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(string->number (list->string first-last-result)))
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(first-last (string->list line) is-numeric-char)))
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(define (solve-all lines)
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(sum (map lines solve-line)))
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(display (solve-all (read-lines)))
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