AdventOfCode-2023-functional/day01-hard/main.scm

#!/usr/bin/guile -s
!#

;=============== functions with side effects (I/O) ======================
(use-modules (ice-9 rdelim))

(define (read-lines)
  ((lambda (line)
    (if (eof-object? line) '() (cons line (read-lines))))
  (read-line)))

(define (display-ln value) (list (display value) (display "\n")))

(define (assert-eq error-message expected actual)
  (if (not (equal? expected actual))
    (display-ln (list error-message (list "expected" expected) (list "actual" actual)))
    '()))

(define (tee value) (car (list value (display-ln value))))
;=============== end of functions with side effects ======================

(define (id value) value)
(define (is-not value) (lambda (x) (not (equal? x value))))
(define (is-not-empty value) (not (null? value)))

;=============== prepend ======================
(define (prepend first-value) (lambda (rest) (cons first-value rest)))

(assert-eq "prepend test failed"
  '(1 2 3 4)
  ((prepend 1) '(2 3 4)))

;=============== combinators ======================
(define (Y f) (f (lambda (x) ((Y f) x))))
(define (Y2 f) (f (lambda (x y) ((Y2 f) x y))))

(assert-eq "Y test 1 (factorial) failed"
  120
  ((Y (lambda (f) (lambda (n) (if (= n 0) 1 (* n (f (- n 1))))))) 5))

(assert-eq "Y2 test 1 (pascal triangle) failed"
  35
  ((Y2 (lambda (f) (lambda (a b)
    (if (= a 0) 1 (if (= b 0) 1 (+ (f (- a 1) b) (f a (- b 1))))))))
    3 4))

;=============== reduce-right ======================
(define (reduce-right initial reducer) (Y
  (lambda (f) (lambda (values)
    (if (null? values) initial (reducer (car values) (f (cdr values))))))))

(assert-eq "reduce-right test 1 failed"
  '(4 101 3 102 2 103 1 104 0)
  ((reduce-right '(0)
    (lambda (current accumulator) (cons (+ 1 (car accumulator)) (cons current accumulator))))
    '(101 102 103 104)))

;=============== map ======================
(define (map mapper) (reduce-right '()
  (lambda (current accumulator) (cons (mapper current) accumulator))))

(assert-eq "map test 1 failed"
  '(1 4 9 16)
  ((map (lambda (x) (* x x)))
    '(1 2 3 4)))

;=============== map ======================
(define (concat left right)
  ((reduce-right right (lambda (current accumulator) (cons current accumulator)))
    left))

(assert-eq "concat test 1 failed"
  '(1 2 3 4 5)
  (concat '(1 2) '(3 4 5)))

;=============== flat ======================
(define flat (reduce-right '() concat))

(assert-eq "flat test 1 failed"
  '(1 2 3 4 5 (6 7) 8)
  (flat '((1 2) () (3 4) (5 (6 7) 8))))

;=============== filter ======================
(define (filter predicate) (reduce-right '()
  (lambda (current accumulator)
    (if (predicate current) (cons current accumulator) accumulator))))

(assert-eq "filter test 1 failed"
  '(2 4 4 2)
  ((filter (lambda (x) (= (modulo x 2) 0)))
    '(1 2 3 4 4 3 2 1)))

;=============== first ======================
(define (first predicate) (reduce-right '()
  (lambda (current accumulator)
    (if (predicate current) current accumulator))))

(assert-eq "first with is-not-empty test 1 failed"
  '(1 2 3)
  ((first is-not-empty) '(() (1 2 3))))

;=============== coalesce ======================
(define (coalesce-not-empty default-lazy) (lambda (value) (if (null? value) (default-lazy) value)))

(assert-eq "coalesce-not-empty test 1 failed"
  '(1)
  ((coalesce-not-empty (lambda () '(1))) '()))

(assert-eq "coalesce-not-empty test 2 failed"
  '(2)
  ((coalesce-not-empty (lambda () '(1))) '(2)))

(assert-eq "coalesce-not-empty test 3 failed (wrong result)"
  '(2)
  ((coalesce-not-empty (lambda () (display-ln "coalesce-not-empty test 3 failed (called default-lazy)")))
    '(2)))

;=============== truthy-chaining ======================
(define (truthy-chaining f) (lambda (value) (if value (f value) #f)))

(assert-eq "coalesce-not-empty test 1 failed"
  2
  ((truthy-chaining (lambda (x) (+ x 1))) 1))

(assert-eq "coalesce-not-empty test 2 failed"
  #f
  ((truthy-chaining (lambda (x) (+ x 1))) #f))

;=============== compose-two ======================
(define (compose-two f g) (lambda (x) (f (g x))))

(assert-eq "compose-two test 1 failed"
  6
  ((compose-two
    (lambda (x) (* x 2))
    (lambda (x) (+ x 2)))
    1))

;=============== compose ======================
(define compose (reduce-right id compose-two))

(assert-eq "compose test 1 failed"
  '(1 2 3 4)
  ((compose (list
    (prepend 1)
    (prepend 2)
    (prepend 3)))
    '(4)))

;=============== compose ======================
(define (combine combiner)
  (lambda (a b) (if (null? a) b (if (null? b) a (combiner a b)))))

(assert-eq "combine test 1 failed"
  '(1 3)
  ((combine (lambda (a b) (list (car a) (car b))))
    '(1 2)
    '(3 4)))

(assert-eq "combine test 1 failed"
  '(1 2)
  ((combine (lambda (a b) (list (car a) (car b))))
    '(1 2)
    '()))

(assert-eq "combine test 1 failed"
  '(3 4)
  ((combine (lambda (a b) (list (car a) (car b))))
    '()
    '(3 4)))

(assert-eq "combine test 1 failed"
  '()
  ((combine (lambda (a b) (list (car a) (car b))))
    '()
    '()))

;=============== sum ======================
(define sum (reduce-right 0 +))

(assert-eq "sum test 1 failed"
  6
  (sum '(1 2 3)))

;=============== repeat ======================
(define (repeat value) (Y
  (lambda (f) (lambda (n)
    (if (= n 0) '() (cons value (f (- n 1))))))))

(assert-eq "repeat test 1 failed"
  '(1 1 1)
  ((repeat 1) 3))

;=============== starts-with ======================
(define starts-with (Y2
  (lambda (f) (lambda (prefix values)
    (if
      (null? prefix)
      values
      (if
        (null? values)
        #f
        (if (equal? (car prefix) (car values))
          (f (cdr prefix) (cdr values))
          #f)))))))

(assert-eq "starts-with test 1 failed"
  '(4)
  (starts-with '(1 2 3) '(1 2 3 4)))

(assert-eq "starts-with test 2 failed"
  '()
  (starts-with '(1 2 3) '(1 2 3)))

(assert-eq "starts-with test 3 failed"
  #f
  (starts-with '(1 2 3) '(1 2)))

(assert-eq "starts-with test 4 failed"
  #f
  (starts-with '(1 2 3) '(4 5 6 7)))

(assert-eq "starts-with test 5 failed"
  (string->list "de")
  (starts-with (string->list "abc") (string->list "abcde")))

;=============== tokenize ======================
(define (tokenize-generic tokens next) (Y
  (lambda (f) (lambda (values)
    (if
      (null? values)
      '(())
      ((compose (list
        (coalesce-not-empty (lambda () (f (cdr values))))
        flat
        (map (lambda (token) ((compose (list
          (map (prepend (car token)))
          (lambda (rest) (if rest (f (next rest values)) '()))))
          (starts-with (cdr token) values))))))
        tokens))))))

(define (tokenize tokens)
  (tokenize-generic tokens (lambda (rest values) rest)))

(assert-eq "tokenize test 1 failed"
  '((101 201) (101 202) (102 201) (102 202))
  ((tokenize '((101 1) (102 1) (201 2) (202 2)))
  '(1 2)))

(assert-eq "tokenize test 2 failed"
  '((101 102 102 101 102))
  ((tokenize '((101 1) (102 2)))
  '(1 2 3 2 1 2)))

(assert-eq "tokenize test 3 failed"
  '((101 102 101) (101 1021) (1012 101))
  ((tokenize '((101 1) (102 2) (1012 1 2) (1021 2 1)))
  '(1 2 1)))

(define (tokenize-aoc tokens)
  (tokenize-generic tokens (lambda (rest values) (cdr values))))

;=============== solution ======================
(define solution-tokens
  (list
    (cons #\0 (string->list "0"))
    (cons #\1 (string->list "1"))
    (cons #\2 (string->list "2"))
    (cons #\3 (string->list "3"))
    (cons #\4 (string->list "4"))
    (cons #\5 (string->list "5"))
    (cons #\6 (string->list "6"))
    (cons #\7 (string->list "7"))
    (cons #\8 (string->list "8"))
    (cons #\9 (string->list "9"))
    (cons #\1 (string->list "one"))
    (cons #\2 (string->list "two"))
    (cons #\3 (string->list "three"))
    (cons #\4 (string->list "four"))
    (cons #\5 (string->list "five"))
    (cons #\6 (string->list "six"))
    (cons #\7 (string->list "seven"))
    (cons #\8 (string->list "eight"))
    (cons #\9 (string->list "nine"))))

(assert-eq "solution tokenize test 1 failed"
  (list (string->list "219"))
  ((tokenize-aoc solution-tokens)
  (string->list "two1nine")))

(assert-eq "solution tokenize test 2 failed"
  (list (string->list "823"))
  ((tokenize-aoc solution-tokens)
  (string->list "eightwothree")))

(assert-eq "solution tokenize test 3 failed"
  (list (string->list "123"))
  ((tokenize-aoc solution-tokens)
  (string->list "abcone2threexyz")))

(assert-eq "solution tokenize test 4 failed"
  (list (string->list "2134"))
  ((tokenize-aoc solution-tokens)
  (string->list "xtwone3four")))

(assert-eq "solution tokenize test 5 failed"
  (list (string->list "49872"))
  ((tokenize-aoc solution-tokens)
  (string->list "4nineeightseven2")))

(assert-eq "solution tokenize test 6 failed"
  (list (string->list "18234"))
  ((tokenize-aoc solution-tokens)
  (string->list "zoneight234")))

(assert-eq "solution tokenize test 7 failed"
  (list (string->list "76"))
  ((tokenize-aoc solution-tokens)
  (string->list "7pqrstsixteen")))

(define solve-line (compose (list
  string->number
  list->string
  (reduce-right '()
    (combine (lambda (left right) (cons (car left) (cdr right)))))
  (map (lambda (char) ((repeat char) 2)))
  car
  (tokenize-aoc solution-tokens)
  string->list)))

(define solve-all (compose (list
  sum
  (map solve-line))))

(display (solve-all (read-lines)))