Passing list to Tcl procedure

list arguments tcl
Juan picture Juan · Oct 20, 2009 · Viewed 23.8k times · Source

What is the canonical way to pass a list to a Tcl procedure?

I'd really like it if I could get it so that a list is automatically expanded into a variable number of arguments.

So that something like:

set a {b c}
myprocedure option1 option2 $a

and

myprocedure option1 option2 b c

are equivalent.

I am sure I saw this before, but I can't find it anywhere online. Any help (and code) to make both cases equivalent would be appreciated.

Is this considered a standard Tcl convention. Or am I even barking up the wrong tree?

Answer

RHSeeger picture RHSeeger · Oct 20, 2009

It depends on the version of Tcl you're using, but: For 8.5:

set mylist {a b c}
myprocedure option1 option2 {*}$mylist

For 8.4 and below:

set mylist {a b c}
eval myprocedure option1 option2 $mylist
# or, if option1 and 2 are variables
eval myprocedure [list $option1] [list $option2] $mylist
# or, as Bryan prefers
eval myprocedure \$option1 \$option2 $mylist

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