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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 list combiner)
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(if
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(null? (car list))
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(cdr list)
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(if
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(null? (cdr list))
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(car list)
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(combiner (car list) (cdr list)))))
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(define (sum numbers) (reduce numbers + 0))
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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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(if
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(null? list)
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'()
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(combine
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(cons
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(if
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(predicate (car list))
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(cons (car list) (cons (car list) '()))
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'())
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(first-last (cdr list) predicate))
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(lambda (current rest)
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(cons (car current) (cdr rest))))))
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(define (solve-line line)
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(
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(lambda (first-last-result) (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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