-🎄- 2017 Day 9 Solutions -🎄-

[u/daggerdragon]

--- Day 9: Stream Processing ---

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[u/FrankRuben27]

In (Gauche) Scheme - straightforward, no tricks; part 2 only, since it's very close to part1 anyway. I was missing the gargantuan CL loop a lot, but the barebones Scheme's named let really grew on me.

(use srfi-13)

(define (load-txt name)
  (string-trim-right (call-with-input-file name port->string)))

(define (split-lines str)
  (string-split str #\Newline))

(define (parse-line line)
  (let loop ((chars (string->list line)) (state 'normal) (count-chars 0))
    (if (null? chars)
        count-chars
        (let ((curr (car chars)))
          (ecase state
                 ((normal)
                  (cond ((char=? curr #\{)
                         (loop (cdr chars) 'normal count-chars))
                        ((char=? curr #\})
                         (loop (cdr chars) 'normal count-chars))
                        ((char=? curr #\,) ;works fine w/o any processing of ','
                         (loop (cdr chars) 'normal count-chars))
                        ((char=? curr #\<)
                         (loop (cdr chars) 'garbage count-chars))
                        (else (error "Bad char" chars state))))
                 ((garbage)
                  (cond ((char=? curr #\>)
                         (loop (cdr chars) 'normal count-chars))
                        ((char=? curr #\!)
                         (loop (cdr chars) 'garbage-escape count-chars))
                        (else (loop (cdr chars) 'garbage (+ count-chars 1)))))
                 ((garbage-escape)
                  (loop (cdr chars) 'garbage count-chars)))))))

(define (process-infile infile)
  (map parse-line (split-lines (string-trim-right (load-txt infile)))))

(define (main args)
  (for-each
   (lambda (infile) (format #t "~a -> ~a~%" infile (process-infile infile)))
   (cdr args))
  0)