Richard Suchenwirth 2005-12-12 - In the Tcl chatroom, CMcC said:
You know, in retrospect, I think [set x a b c] should be equivalent to [set x [list a b c]]
Well, Tcl is where wishes come true :) Here's my experimental code that overloads set, and seems to work fine, as far as I've tested. I had to reuse the _var name for upvar, so the error message comes right if the variable doesn't exist yet:
rename set _set
proc set {_var args} {
upvar 1 $_var $_var
_set ll [llength [info level 0]]
if {$ll==3} {
_set $_var [lindex $args 0]
} elseif {$ll>3} {_set $_var $args}
_set $_var
}Lars H: Ehh... Why this insanely complicated solution? The user-supplied name for a local variable is just asking for trouble -- consider what happens for [set ll]!! The straightforward solution is rather:
proc set {varname args} {
upvar 1 $varname var
if {[llength $args] == 0} then {
return $var
} elseif {[llength $args] == 1} then {
_set var [lindex $args 0]
} else {
_set var $args
}
}RS: It is to avoid the misleading error message below - but I agree that variable ll opens a vulnerability, so your code is safer.
% set foo can't read "var": no such variable
Ingemar H: The above small problem is easily solved by this:
if {[llength $args] == 0} then {
if {[info exists var]} {
return $var
} else {
_set $varname
}The distinction between $ll==3 and $ll>3 is necessary so this frequent case comes right:
set something {}Testing:
% source myset.tcl
% set foo
can't read "foo": no such variable
% set foo 1
1
% set foo
1
% set bar 2 3 4
2 3 4
% set bar
2 3 4
% set grill {{}}
{}
% set grill
{}
% set nix {}
% set nix
%So far it looks as expected. But bytecode compilation may lose performance if a fundamental like set is pulled from under its feet...