advent-of-code-2022/day-06/part-01.scm

(import
 (except (rnrs base) let-values map)
 (only (guile)
       lambda* λ
       string-split
       string-count
       string-every
       string-append
       list->string)
 (fileio)
 ;; (srfi srfi-1)
 ;; (srfi srfi-8)
 ;; (srfi srfi-11)
 (ice-9 pretty-print)
 (ice-9 match))


(define lines (get-lines-from-file "input"))
(define input (car lines))

(define unique-chars?
  (λ (str)
    (string-every (λ (c) (= (string-count str c) 1))
                  str)))

(define buffer-len 4)

(let iter ([pos 0] [input° input])
  (cond
   [(string-null? input°)
    'done]
   [else
    (let ([part (substring input° 0 buffer-len)])
      (cond
       [(unique-chars? part)
        (pretty-print part)
        (pretty-print input°)
        (+ pos buffer-len)]
       [else
        (iter (+ pos 1)
              (substring input° 1))]))]))