s c h e m a t i c s : c o o k b o o k

(define (countlines filename)
  (call-with-input-file filename
    (lambda (p)
      (let loop ((line (read-line p))
                 (result 0))
        (if (eof-object? line)
            result
            (loop (read-line p) (+ 1 result)))))))

(define (fold-file-lines filename knil kons)
(call-with-input-file filename
    (lambda (p)
      (let loop ((line (read-line p))
                 (result knil))
        (if (eof-object? line)
            result
            (loop (read-line p) (kons line result)))))))

(define (countlines fname) 
  (fold-file-lines fname 0 
                   (lambda (line result) (+ 1 result))))

(define (readlines fname) 
  (reverse 
   (fold-file-lines fname '() cons)))

(define count-lines 
  (let ([re (regexp ".*?((\n\r)|(\r\n)|\n|\r|$)")])   ; *? shortest possible
    (lambda (filename)
      (call-with-input-file filename
        (lambda (in)
          (let loop ([l 0])
            (cond
              [(eof-object? (peek-char in))  l]
              [(regexp-match re in)          (loop (+ l 1))]
              [else                          (loop l)])))))))