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
For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
Array elements inside proc

Posted by Arshad (Arshad), 3 January 2008
I am able to add an element to the array using the reference addr but I cannot print it or copy it to any other variable. This seems to be a bit surprising !!

proc foo {in} {
   upvar in addr
   puts $addr(3)

for {set count 1} {$count <= 4} {incr count} {
   set sa($count) $count
foo sa;

can't read "addr(3)": no such variable
parray sa;

Posted by admin (Graham Ellis), 3 January 2008
In Tcl, you must use a dollar sign if you want to refer to the contents of a variable, but you do not use a dollar sign if you are setting the value, or doing both at in the same context.

So you probably meant

upvar $in addr

and not

upvar in addr

since in the the name of the array that is passed in to the proc and is only used (and not set) within the upvar command, even if the array who's name it refers to may be set.

When I'm running a Tcl course, I always find myself spending longer on upvar than any other command.   And judging by the number of questions on it that I get here from people I have not trained, I think it's one of those things a lot of people need help with!

This page is a thread posted to the opentalk forum at 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., 2022: Well House Manor • 48 Spa Road • Melksham, Wiltshire • United Kingdom • SN12 7NY
PH: 01144 1225 708225 • FAX: 01144 1225 793803 • EMAIL: • WEB: • SKYPE: wellho