Setting A Variable Number Of Global Variables

[cptk]

At startup, the application reads in a text file and uses some of the settings to help create Checkboxes within a grid. The text file contents can vary, thus the number of checkboxes created will vary as well. The checkboxes are built in the main portion of the program (i.e. -outside of any proc), but I need to use their -variable option value in a proc, thus I need to globally set each of the checkboxe's -variable options within the proc. HOW DO YOU WORK WITH VARING NUMBER OF VARIABLES GLOBALLY? ...thanks!

 

[cptk]

I've gotten closer (thanks to a previous search and reply from "ULIS&quot, but ...

I can't seem to finalize it!!

How do I "build" a variable using the "::"?
Ex: $::cbv$w
where $w equals "OPT1"
- it gives me an error "can't read "::cbv"; no such variable

Hardcoding the $::cbvOPT1 works great though.

 

[Bong]

I would use list and lappend:

read the text file into a list of variable names, say, vlist
then:

foreach var $vlist {lappend globalst cbv$var}

then, in your proc:
global gblst
eval global $gblst


Bob Rashkin
rrashkin@csc.com

 

[Bong]

I meant:
foreach var $vlist {lappend gblst cbv$var}
sorry:-(



Bob Rashkin
rrashkin@csc.com

 

[cptk]

Thanks, but I tried that and it's not giving me what I need.

That method still requires me to set value explicitly, like:
$::cbvOPT1

What I want to do is to be able to subsitute a portion of the global variable, like $::cbv$w
This should be easy, but I'm "blocked" right now ...

 

[oldtimer47]

I assume you need to use the global -onvalue value of a checkbox?

I think this might resolve your problem, provided you incorporate Bong's advice.

> global gblst
> eval global $gblst

> foreach x $gblst {
> .info_display insert end "[expr $$x]\n"
> }

By the way, if you use instead "eval" in place of "expr", it will attempt to execute the return value of the -onvalue(due to the []'s), which is not what you exactly need. Here, the expr gives you what you need. I never could figure the difference betw. the two, if someone could elaborate, fell free. Hope this helps!

 

[ulis]

You can set easily a variable with a composed name:

set ::cbv$w 1234

But, for referencing it, you need a more complex syntax because this doesn't work:

set a $::cbv$w

With such a line Tcl searches for the value that is the concatenation of the values of the global variable ::cbv and of the local variable w. Not for the value of the global variable ::cbv$w (whose name is the concatenation of the string ::cvb with the value of w).
In other words, Tcl sees [$::cbv][$w} and not $[::cbv$w].
To do the trick you need to use the old syntax to get the value of your variable with a composed name:

set a [set $::cbv$w]

From the manual page:

set varName ?value?
Returns the value of variable varName. If value is specified, then set the value of varName to value, creating a new variable if one doesn't already exist, and return its value.

HTH

ulis

 

[ulis]

Sorry, I should say:

set a [set ::cbv$w]

ulis

 

[AviaTraining]

This is really much easier if you use a global array rather than separate global variables. The -variable attribute can accept an element of a global array (as can the -textvariable attribute supported by many widgets and the -listvariable attribute supported by the listbox). Then you have a single global declaration in your procedures. For example:

checkbutton .cb1 -text "Choice 1" -variable values(val1)
checkbutton .cb2 -text "Choice 2" -variable values(val2)
checkbutton .cb3 -text "Choice 3" -variable values(val3)
checkbutton .cb4 -text "Choice 4" -variable values(val4)
checkbutton .cb5 -text "Choice 5" -variable values(val5)
pack .cb1 .cb2 .cb3 .cb4 .cb5

proc myProc {} {
  global values
  foreach elem [lsort [array names values]] {
    puts "values($elem) = $values($elem)"
  }
}

- Ken Jones, President, ken@avia-training.com
Avia Training and Consulting,

http://www.avia-training.com

866-TCL-HELP (866-825-4357) US Toll free
415-643-8692 Voice
415-643-8697 Fax

 

[cptk]

Ken -
That's almost what I did while experimenting over the weekend. I already have a "two-dimensional" opt_array set-up, so all I did was add another element (i.e. - CBstate) to that array when I set the -variable value of the checkbox widget.
> foreach $x $option_list
> -variable opt-array($x, CBstate)

Since opt_array is defined outside any proc stmt (what do you typically call this area when it's outside any procs - main area?) and I'm also defining the checkboxes outside the main area, when I need to see the "state" of a checkbox within a proc, I just refer to the global opt_array variable, which will have the CBstate element. This keeps it simple and efficient!
Thanks for the response ...

 

[AviaTraining]

I usually refer to code outside of any procedures as being in the global scope. (Unless it's inside of a namespace block, in which case I cringe a bit and call it the namespace scope because I don't know what else to call it.) I'm not a formal computer linguist, so I don't get too hung up on the terms I'm using as long as everyone knows what I'm talking about.

As an aside for those people who might not be aware of it, it's legal for a Tcl procedure to create a new global variable. For example:

proc init {} {
    global state
    set state "disconnected"
}

# ...

init

This is particularly handy for libraries of Tcl code, when you need to initialize the state of the library code before executing other library procedures. Also, I know that some programmers who come from a C/C++ background like to create a main procedure in their Tcl code, and then explicitly call main to start their application running.

This can actually provide a slight performance advantage, especially if you've got one or more loops that will run many iterations. Tcl procedures are bytecode-compiled, and thus they can run faster than global, uncompiled code. But it doesn't make much difference unless there's a lot of code to run, like the long loops I mentioned above:

% time {
    for {set i 0} {$i < 100000} {incr i} {
        lappend list1 [expr { rand()*20000 - 10000 }]
    }
}
310138 microseconds per iteration
% proc init {} {
    global list2
    for {set i 0} {$i < 100000} {incr i} {
        lappend list2 [expr { rand()*20000 - 10000 }]
    }
}
% time { init }
165162 microseconds per iteration

- Ken Jones, President, ken@avia-training.com
Avia Training and Consulting,

http://www.avia-training.com

866-TCL-HELP (866-825-4357) US Toll free
415-643-8692 Voice
415-643-8697 Fax