Using Tcl to trace changes to array variables

The Tcl trace command can be used to respond to changes to variables occur, these changes are array, read, write and unset.

When one of these events occurs, a sub-script is execute and a number of values passed to it. In the case of an array operation, these are the array name, the member, and the operation.

Following this it is then possible, with a bit of string splicing, to obtain the value of the value of the changed array member.

Example:

proc AAA {args} {
   lassign $args a b c
   puts [set ${a}($b)]
   }

trace add variable ::conze::editor::block write AAA
set ::conze::editor::block(::gnocl::_WID26_,start) 5

Comments

gnocl::calendar

Given this module some attention today. Added some of the more package wide options to the module and created customised handler for setting the month. (For some odd reason months are are counted 0-11 whereas days are 1-31.) There's still a little more to do to this one including the addition of code to store diary details. Here's the working test script to show the range of options at work. The percentage substitution string item %e explores something that I've been toying with, the name of the signal/event that initiated the call. Ok, a script can keep its own internal trace but who knows, it might prove useful. #--------------- # calendarTest.tcl #--------------- # Author: William J Giddings # Date: 07/05/09 #--------------- #!/bin/sh # the next line restarts using tclsh \ exec tclsh "$0" "$@" #--------------- package require Gnocl set cal [gnocl::calendar] $cal configure -day 8 -month 7 -year 1956 $cal configure -rowHeight 1 -colWidth 1 $ca

Gnocl Dashboard

Over the past few programming sessions I've been working on producing a central point, a dashboard, around which it's possible to see the various Gnocl widgets and commands in operation. In many ways like the demo script which shipped with the earlier releases of Gnocl but offers much more. The introspection functionality provides details of the various options and sub-commands of each Gnocl procedure which are displayed under the associated tab. Sample scripts are included for each item which offers newcomers a clearer insight into how make the most of what's on offer.

Simple Runtime Debugging Message Dialog

At times it's useful to see what values variables hold, or offer some pause point before the code goes elsewhere before causing havoc. Its possible to write output to the terminal but this can get lost in copious forms of other outputs, besides, there's no pausing the script execution either. The following proc creates a custom dialog which displays ad message along with the point in the calling script from which it was invoked. ## simple runtime debugging feedback dialog, alternative to console based gnocl::msg # @param msg message to display # @returns none # proc xxx::msg {txt} { set frame [info frame -1] append msg "Message:\n\n" append msg " $txt \n\n\n" append msg "Called from:\n\n" append msg "Proc:\t[lindex [info level -1] 0]\n" append msg "File:\t[file tail [dict get $frame file]]\n" append msg "Line:\t[dict get $frame line]\n" gnocl::dialog \ -type info \ -text $msg

Gnocl -the Tcl/Gtk Bindings

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