[Xotcl] Passing a switch non-positional argument

From: Kurt Stoll <kstoll_at_echelon.com>
Date: Wed, 1 Mar 2006 22:28:24 -0000

 

I suppose this is a trivial question, but I find this annoying.

 

Is there an easy was of passing a switch non-positional argument to another
procedure based upon the value provided to the calling procedure? For
example, if both p1 and p2 take a switch non-positional argument -sw, and p2
calls p1, but wants to forward along the state of the -sw parameter, how is
that best expressed. The straightforward approach - testing the value of
-sw and then using the correct invocation - is ugly, and subject to
combinatorial explosion. To avoid the combinatorial problems, and make it a
little cleaner, I can collect the options in a list and then make the call
(using an eval). This works, and is certainly cleaner, but it still seams
that there should be an easier way to pass the value along; passing other
options along is simply a matter of calling the option and providing the
current value. The example below shows these options:

 

Object obj

 

obj proc p1 {{-sw:switch 0} {-opt 1}} {

    puts "sw: $sw"

    puts "opt: $opt"

}

 

obj proc p2 {{-sw:switch 0} {-opt 1}} {

    if { $sw } {

        my p1 -sw -opt $opt

    } else {

        my p1 -opt $opt

    }

}

 

obj proc p3 {{-sw:switch 0} {-opt 1}} {

    set options [list -opt $opt]

    if { $sw } { lappend options -sw }

    eval my p1 $options

}

 

Is there a better way to do this?

 

Thanks,

Kurt