tk again (question)

[Tim Writer]

"Peter L. Peres" <plp-ysDPMY98cNQDDBjDh4tngg at public.gmane.org> writes:

> On Mon, 1 Mar 2004, Tim Writer wrote:
> 
> --snip--
> >
> > The format of the list returned by itemconfigure is documented (more or less)
> > by "man Tk_ConfigureInfo".  This should help:
> >
> >     # This first part is identical to your script
> >     set c .c
> >     canvas $c
> >     pack $c
> >     $c create rectangle 10 10 20 20 -fill blue -tags {one two}
> >     set o [$c itemconfigure 1]
> >
> >     # Now create a script to create another rectangle with same attributes
> >     set script [list $c create rectangle 30 30 40 40]
> >     foreach configSpec $o {
> >         foreach {argvName dbName dbClass defValue curValue} $configSpec {}
> >         lappend script $argvName $curValue
> >     }
> >
> >     # Create new rectangle
> >     eval $script
> 
> This is clear. Now I understand that I only need to record those options
> which are different from default to recreate the options, so I could
> write:
> 
> 	...
> 	foreach configSpec $o {
> 		foreach {argvName dbName dbClass defValue curValue} \
> 			$configSpec {} {

Careful!  You have an extra set of braces above.  This:

    foreach {argvName dbName dbClass defValue curValue} $configSpec {}

is the same as:

    foreach {argvName dbName dbClass defValue curValue} $configSpec {
        # do nothing
    }
  
which is a shorthand (idiomatic Tcl) for:

    set argvName [lindex $configSpec 0]
    set dbName [lindex $configSpec 1]
    set dbClass [lindex $configSpec 2]
    set defValue [lindex $configSpec 3]
    set curValue [lindex $configSpec 4]

If this was Perl, you might write:

    my ($argvName, $dbName, $dbClass, $defValue, $curValue) = @configSpec;

> 			# not sure about != {} or != "" - should be the same
> 			if {($curValue != {}) && ($defValue != $curValue)} {
> 				lappend script $argvName $curValue
> 			}

I would just write:

    if {$curValue != $defValue} {
        lappend script $argvName $curValue
    }

With your test, if $curValue is {} and $defValue is something other than
{}, you don't record it.

-- 
tim writer <tim-s/rLXaiAEBtBDgjK7y7TUQ at public.gmane.org>                                  starnix inc.
905.771.0017 ext. 225                           thornhill, ontario, canada
http://www.starnix.com              professional linux services & products
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