RE's and Hashes

StuPeas posted this at 10:43 — 12th August 2006.

Joined: Oct 2004

Hi
I'm learning perl and have hit problems fairly early on. I have typed a program into perls editor that is suppost to determine the frequency of the occurence of each word in a string.

Once i have saved the program and run it i get a warning about a variable being used only once. If i proceed and type in the string "One Two Two Three" (without the quotes), nothing happens and the programme wont exit. the only way to get out of it is to close down the MS DOS window. i have written the code below, i would be greatfull if somebody could tell me the problem with it.
It would be realy helpful to know why this doesnt work, and not to recieve any advice on programs that would do the same thing.

THANX

#!C:\perl\bin\perl.exe
 
while ($line = <STDIN> ) 
{
     while ($line =~ s/(\w+)(.*)/$2/)
   {
     $word = $1;
     $wordHash{$word}++;
   }
 }

while ( ($word, $count) = each(%wordHash) )
{
   $wordArray[$i] = "$word\t$count";
   $i++;
   print ("$word\n");
 }
 

whitehawk posted this at 19:22 — 27th August 2006.

She has: 2 posts

Joined: Aug 2006

In your regular expression, /(\w+)(.*)/$2/), the (.*) bit will match everything, therefore never end (note that regular expressions are greedy, and will match the longest possible string).

What you probably want is something more like
([a-zA-Z]*) or (\w*) (match any alphabetic characters)
OR (([^\s]*) i.e. match anything that's not whitespace.
OR you could use the word boundary thingie, \b ... eg ... (\b.*\b).

I haven't tried either of these out, but you get the general idea.

Cheers,
Julie

whitehawk posted this at 19:23 — 27th August 2006.

She has: 2 posts

Joined: Aug 2006

D'oh! Just noticed the date on the post I just replied to ... think I might be a bit late to help!!