"You can acheive in 20 lines of Tcl/Tk something that would take twice that using another GUI system." That claim might be a bit aggressive, but here is a tiny Tcl/Tk example to lay out a numeric data entry pad, allow it to stretch, and also provide an example of upvar (always worth providing an example ... not an easy concept for newcomers!)




proc play val {
upvar $val current
set colours {red green yellow blue}
incr current
set current [expr $current % [llength $colours]]
return [lindex $colours $current]
}

set chess 0
label .res -text result -background [play chess]
grid .res - - -sticky news
set rowz {1 2 3 4 br 6 7 8 9 * 0 #}
set rn 0
foreach {a b c} $rowz {
incr rn
label .a$rn -text $a -background [play chess]
label .b$rn -text $b -background [play chess]
label .c$rn -text $c -background [play chess]
grid .a$rn .b$rn .c$rn -sticky news
}
grid rowconfigure . {0 1 2 3 4} -weight 1 -minsize 40
grid columnconfigure . {0 1 2} -weight 1 -minsize 40


Link - Procedures, upvar and variable scope
Link - Tk Window Manager Examples
(written 2005-02-12, updated 2006-06-05)

 T218 - Tcl/Tk - Geometry Managers
  [1470] fill and expand on Tcl/Tk pack command - (2007-12-13)
  [1340] Tk locks up - 100% c.p.u. on a simple program (Tcl, Perl, Python) - (2007-09-09)
  [1335] Expanding a grid - Tcl/Tk - (2007-09-07)
  [787] Tk - laying out your GUI with frames, pack and grid - (2006-06-30)
  [445] Sticky news - (2005-09-15)

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Cheap purchase - votes paid for with selfish promises
Open Source becomes mainstream
Futility of war?
Off to Munich
Tcl/Tk (wish) Grid layout example
Look after your staff and they'll look after you. AOL.
Joining lists in Tcl. Indirect variables in Tcl.
FAQ - Perl or PHP
Examples - Gadfly, NI Number, and Tcl to C interface
Canteen Dragon