#!/usr/bin/guile \
-e main -s
!#
;;; Copyright 2005 Daniel Cer (daniel.cer@cs.colorado.edu)
;;;
;;; This work is licensed under the Creative Commons Attribution-NonCommercial-
;;; ShareAlike License. To view a copy of this license, visit 
;;; http://creativecommons.org/licenses/by-nc-sa/2.5/ or send a letter to 
;;; Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 
;;; 94105, USA.

;; routine to read in entries from an input-port
(define (read-entries input-port) 
  (let ((in-line (read-line input-port)))
    (if (eof-object? in-line) '() 
      (append (list (string->number in-line)) (read-entries input-port)))))

;; routine to find the minimum entry in a vector that has an index that is
;; greater than or equal to start-idx
(define (find-min entries start-idx) (do ((idx (+ start-idx 1) (+ idx 1)) 
  (min-idx start-idx 
  (if (< (vector-ref entries idx) (vector-ref entries min-idx)) idx min-idx))) 
  ((equal? idx (vector-length entries)) min-idx) '() ))

;; performs a selection sort on a vector of items
(define (selection-sort entries) (do ((idx 0 (+ idx 1))) 
  ((equal? idx (vector-length entries)) entries)
  (let* ((min-idx (find-min entries idx))       ; find the minimum vector val
        (min-val (vector-ref entries min-idx))) ; with an index >= idx
  (vector-set! entries min-idx (vector-ref entries idx)) ; swap idx-th entry
  (vector-set! entries idx min-val))))                   ; with min-idx entry

(define (main args) 
  (if (not (equal? (length args) 2)) 
    (display 
    (string-append "Usage:\n\t" (car args) " (file with numbers to sort)\n"))
    (map (lambda (x) (display x) (newline))   ; display the sorted entries
       (vector->list (selection-sort          ; perform the selection sort
          (list->vector                       
             (call-with-input-file 
             (car (cdr args)) read-entries))))))) ; read in the entries