Training, Open Source computer languages
PerlPHPPythonMySQLApache / TomcatTclRubyJavaC and C++LinuxCSS 
Search for:
Home Accessibility Courses Diary The Mouth Forum Resources Site Map About Us Contact
Context

Posted by admin (Graham Ellis), 22 December 2002
Perl uses the concept of "context" to work out what to do with a list - if you write @stuff in your code, it depends whether it's somewhere that a list actually makes sense (in which case the list is used), somewhere where a list does not make sense (in which case Perl uses the length of the list), or in double quotes (in which case Perl concatenates all elements of the list with a copy of the variable $" - default a space character - between each).

Here's a sample piece of code that I wrote during the Perl course I was running last week - I think I had the opportunity to add a few comments for once!

Code:
@stuff = (10,"twenty",30,"forty");

@morestuff = @stuff;   # take copy of list
$stuffabout = @stuff;   # you must mean the LENGTH of the list!

print @stuff,"\n";
print @morestuff,"\n";
print $#morestuff,"\n";         # 3 (0 to 3)
print $stuffabout,"\n";         # 4 (there are 4 elements)

($first,$second,$third,$next) = @stuff;
print "$next $second $first $third\n";

($oneth, @rest) = @stuff;       # 10 into $oneth, rest into @rest
print @rest,"\n";               # No spaces
print "@rest\n";                # Space between each
print @rest+0,"\n";             # Scalar - print the length

($stuffab) = @stuff;    # force list context.  1st element!
print $stuffab,"\n";





This page is a thread posted to the opentalk forum at www.opentalk.org.uk and archived here for reference. To jump to the archive index please follow this link.

You can Add a comment or ranking to this page

© WELL HOUSE CONSULTANTS LTD., 2014: Well House Manor • 48 Spa Road • Melksham, Wiltshire • United Kingdom • SN12 7NY
PH: 01144 1225 708225 • FAX: 01144 1225 899360 • EMAIL: info@wellho.net • WEB: http://www.wellho.net • SKYPE: wellho