(define-module (aoc-utils)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-9)
  #:use-module (ice-9 regex)
  #:use-module (ice-9 rdelim)
  #:export (file->list
            lines->number-list))

(define (file->list filename)
  (let ((lines (string-split (call-with-input-file filename read-string) #\Newline)))
    ; Remove EOF token
    (take lines (1- (length lines)))))

(define (lines->number-list lines)
  (map (lambda (line)
         (map string->number (string-split line #\Space)))
       lines))

(define (remove-nth l n)
  "Remove the `N' element from `L', returning a new list."
  (append (list-head l n) (list-tail l (1+ n))))

(define (indexes lst)
  "Get the indexes for `lst'."
  (let ((retval '()))
    (do ((i (1- (length lst)) (1- i)))
        ((< i 0))
      (set! retval (cons i retval)))
    retval))