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@ -22,14 +22,14 @@ |
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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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(define (combine a b combiner) |
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(if |
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(null? (car list)) |
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(cdr list) |
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(null? a) |
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b |
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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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(null? b) |
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a |
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(combiner a b)))) |
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(define (sum numbers) (reduce numbers + 0)) |
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@ -43,22 +43,20 @@ |
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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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(repeat (car list) 2) |
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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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(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) |
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(cons (car current) (cdr rest))))) |
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'())) |
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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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((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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