#! /bin/sh
#| Hey Emacs, this is -*-scheme-*- code!
#$Id$
exec mzscheme -u "$0" ${1+"$@"}
|#
#lang scheme
(require "../prelude.ss")
; (string->string) -> string -> string -> #<void>

(define (interact-with f in out)
  (with-output-to-file out #:mode 'text #:exists 'replace
    (λ () 
      (with-input-from-file in 
        (λ ()
          (let next-line ([line (read-line)])
            (cond [(eof-object? line) (void)]
                  [else (write-string (f line))
                        (newline)
                        (next-line (read-line))])))
            #:mode 'text))))

; char -> boolean
(define char-nonspace? (compose not char-whitespace?))

; string -> string
(define (first-word line)
  (list->string
   (take-while char-nonspace? 
               (drop-while char-whitespace? (string->list line)))))
                    
;; Program execution starts here
(define (main)
  (define arguments (current-command-line-arguments))
  (if (= (vector-length arguments) 2)
      (let ([in  (vector-ref arguments 0)]
            [out (vector-ref arguments 1)])
        (interact-with first-word in out))
      (error "interact-with expects exactly 2 arguments  : interact-with in-file-path out-file-path\n\tProvided : " arguments)))

(main)