aoc2020/18.rkt

#lang curly-fn racket

(require "scripts/aoc.rkt" parser-tools/lex parser-tools/yacc (prefix-in : parser-tools/lex-sre))

;; solution for day 18

(define-tokens nums [number])
(define-empty-tokens syms [+ * lp rp eof])

(define oo-lexer
  (lexer
    [whitespace (oo-lexer input-port)]
    ["+" (token-+)]
    ["*" (token-*)]
    ["(" (token-lp)]
    [")" (token-rp)]
    [(:+ (char-set "0123456789")) (token-number (string->number lexeme))]
    [(eof) (token-eof)]))

(define-simple-macro (make-oo-parser/precs needed-precs ...)
  (parser
    [start exp]
    [end eof]
    [error (lambda args (error "not shonks:" args))]
    [tokens nums syms]
    [precs needed-precs ...
           (left lp rp)]
    [grammar
      (exp [(lp exp rp) $2]
           [(exp + exp) (+ $1 $3)]
           [(exp * exp) (* $1 $3)]
           [(number) $1])]))

(define (parse/string oo-parser str)
  (let ([input (open-input-string str)])
    (oo-parser (thunk (oo-lexer input)))))

(define-simple-macro (define-part name:id needed-precs ...)
  (define (name input)
    (for/sum ([line (in-list input)])
      (parse/string (make-oo-parser/precs needed-precs ...) line))))

(define-part part1 (left + *))
(define-part part2 (left *) (left +))

(define parse file->lines)

(module+ main
  (define input (parse "inputs/18"))
  (answer 18 1 (time (part1 input)))
  (answer 18 2 (time (part2 input)))
  (displayln "meow"))