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From: composer@chem.bu.edu (Jeff Kellem)
Newsgroups: comp.lang.perl
Subject: Re: Need clarification of assoc. arrays
Message-ID: <COMPOSER.91Jan30141424@chem.bu.edu>
Date: 30 Jan 91 19:14:24 GMT
References: <7457@aspect.UUCP>
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Organization: Boston University Chemistry Department
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In-reply-to: dave@aspect.UUCP's message of 28 Jan 91 22:09:25 GMT

In article <7457@aspect.UUCP> dave@aspect.UUCP (Dave Corcoran) writes:
>
>   Date: 28 Jan 91 22:09:25 GMT
>
>   printf("Hello world\n");

print 'Hello world\n';	# if (a tiny bit) quicker  ;-)

>   Why is does this script:
>
>	   perl -e '
>		   $keyword{"one"}="ONE";
>		   $keyword{"two"}="TWO";
>
>		   for $i (%keyword) {
>			   print $i;
>		   }'
>   yield
>	   twoTWOoneONE
>   and not 
>	   onetwo	

An associative array is stored as a LIST of

	( key, value, key, value, ... )

So, when you just access it as %keyword, you're getting a LIST of the above.
If you just want the keys (indices) of the assoc. array, do...

	for $i (keys %keyword) { ... }
or
	for $i (sort keys %keyword) { ... }

if you want to access the assoc. array sorted by the keys.  To access just the
values assoc. array, use `values':

	for $value (values %keyword) { ... }

or to access both key/value pairs from the assoc. array:

	while (($key, $value) = each %keyword) { ... }

Take a look at the man page entries for `keys', `values', and `each'.

>   I am trying to print the indices and the contents of the array thus:
>
>	   for $i (%keyword) {
>	      printf "the index is %s; the contents are %s\n",$i,$keyword{$i};
>	   }

So, this should be written as

	for $i (keys %keyword) {
	    print "the index is $i; the contents are $keyword{$i}\n";
	}

Use `print' instead of `printf' when you can; it is a tiny bit faster.

Hope that helps..Enjoy Perl!

			-jeff

Jeff Kellem
Internet: composer@chem.bu.edu