Erik Naggum wrote:

> | This isn't meant to reopen the great LOOP flame war but one way of
> | doing it is:
> |
> | (with-open-file (ifile "key.html" :direction :input)
> | (loop for line = (read-line ifile nil)
> | while line
> | counting 1))
>
> Simply using while (read-line ifile nil nil) seems even more compact.
>
> However, I have this negative gut reaction to wanton waste, as in
> effectively allocating as many strings as there are lines for no
> good reason, just exercising the garbage collector, so while we're
> at it, how about
>
> (loop for char = (read-char ifile nil nil)
> while char
> count (char= char #\newline))
>
> Note that read-line will return nil on an empty file, but the data
> leading up to the end-of-file if no newline intervened and then nil
> on the next call, effectively counting a non-empty file containing
> no newlines as having one line. This may be relevant.
>
> | (loop for line being each line of ifile
> | count 1)
>
> Elegant.

Gauche Scheme

(generator-count identity read-line)

Testing:

(use gauche.generator)

(with-input-from-string
"one
two
three"
(lambda _ (generator-count identity read-line)))

===>
3