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Christopher Browne  
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 More options Jun 23 2000, 3:00 am
Newsgroups: comp.lang.lisp
From: cbbro...@news.hex.net (Christopher Browne)
Date: 2000/06/23
Subject: Re: Newbie asking for help
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Centuries ago, Nostradamus foresaw a time when The Glauber would say:

>In article <8iti9v$d1...@nnrp1.deja.com>, glauber wrote:
>[...]
>> ;; count number of lines in file key.html
>> (with-open-file (ifile "key.html" :direction :input)
>>                 (setf nlines 0)
>>                 (loop
>>                   (if (read-line ifile nil)
>>                     (setf nlines (+ 1 nlines))
>>                     (return nlines))))

>> It doesn't work (it just hangs, so i think it's stuck in the loop). I
>[...]

>OK. Using TRACE, i found that read-line wasn't returning nil, but
>something like #<END-OF-FILE>. So i added the third optional parameter,
>the one that tells it what to return at end of file. This made me do
>the (IF) backwards:

#<END-OF-FILE> may be "pretty cool," but certainly isn't conformant
with the standard.

>;; count lines
>(with-open-file (ifile "key.html" :direction :input)
>                (setf nlines 0)
>                (loop
>                  (if (eql 'eof (read-line ifile nil 'eof))
>                    (return (print nlines))
>                    (setf nlines (+ 1 nlines)))))

>And it works...

>And, of course, this works too:

>(with-open-file (ifile "key.html" :direction :input)
>                (setf nlines 0)
>                (loop
>                  (if (read-line ifile nil nil)
>                    (setf nlines (+ 1 nlines))
>                    (return (print nlines)))))

>So, i plod along, undaunted...
>I'm pretty sure this is an ugly program, and i appreciate suggestions.

I somewhat like the following:
(with-open-file
 (ifile "c:/home/html/lynx-boo.htm" :direction :input)
 (loop
  for line = (read-line ifile nil 'eof)
  for lines = 0 then (+ lines 1)   ;;; Line count...
  until (eql line 'eof)
  finally (return lines)))

The use of "for" clauses has the merit of eliminating the extra
control structures inside the loop.
--
cbbro...@acm.org - <http://www.ntlug.org/~cbbrowne/lsf.html>
Rules of the Evil Overlord #132. "Before appointing someone as my
trusted lieutenant, I will conduct a thorough background investigation
and security clearance. <http://www.eviloverlord.com/>


 
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