Is there any way to pass a list to a proceedure?

[rubberscissors]

I'm calling a proceedure that needs to be passed a series of variables, and I want one of the variables passed to be a list.

Basically, I have a while loop and for each iteration of the loop at one point it checks a series of radiobuttons and makes a list based on each one which has been selected. So, the list varies in length and content, but each iteration also calls a proceedure which will make use of the elements on the list...I want to pass the list to the proceedure at each iteration of the loop...is there a way to do this? Each time I try, it complains there is 'no such variable'...which I think is because it's not a variable but a list. Any thoughts?

 

[marsd]

set R_list {
"elementone"
"element two"
"elementthree"
}
set e 0
proc bogus {var var_list} {
global e
while {[button_button] > 0} {
foreach elem [lsort $var_list] {
puts "$elem is part of $var_list."
if {[string compare $elem $var] == 0} {
upvar #0 $elem mat[incr e]
}
}
}
}

bogus elementone $R_list

This is a bs example but it details that you can process
the output of a fictional procedure that reads data from
buttons > 0 ; sorts the list data and then compares them to declared string var.
If matching the list element var is declared in the global scope. In theory.
I have never had any luck with upvar #0, but the info on upvar is worth reading to understand the stack levels.

Maybe one of the big wigs can help you more.

 

[AviaTraining]

Well, the simple answer is that there's no problem passing a list as an argument to a procedure. For all practical purposes, a list is simply a white-space separated sequence of elements stored as a string. (It's actually handled a bit more efficiently in the Tcl internals, but that's the way you should regard lists from a scripting point of view.) So, anywhere you could pass a string, you could also pass a list.

Here's a simple example:

proc lreverse { list } {
    set newlist {}
    set i [llength $list]
    for { incr i -1 } { $i >= 0 } { incr i -1 } {
        lappend newlist [lindex $list $i]
    }
    return $newlist
}

This defines lreverse as a procedure that accepts one argument, which happens to be a list. The list provided as an argument is stored in the variable list. (Note that I didn't have to choose the name "list"; it could have been any variable name at all.) Here's a couple examples of calling this procedure interactively:

[tt]% lreverse {one two three four}
four three two one
% set states [ignore][list California "New York" Indiana][/ignore]
California {New York} Indiana
% lreverse $states
Indiana {New York} California[/tt]

In both cases, I'm passing a single argument to lreverse, but the argument happens to be a list. - Ken Jones, President
Avia Training and Consulting

http://www.avia-training.com

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