Static variable in Tcl

Question

Is it possible to declare a static variable in Tcl?
I use a specific function to detect unknown command errors, and I want it to print an error message the first time an unknown command appears, so I need to save something like a static list inside proc . Is it possible?

Answer 1

Or you can just use a direct global variable:

 set varList {} proc useCount {value} { global varList ; lappend varList $value } useCount One useCount Two puts $varList 

Answer 2

Not. But you can use a global (usually named) array indexed by proc, for example:

 namespace eval foo { variable statics array set statics {} } ... proc ::foo::bar args { variable statics upvar 0 statics([lindex [info level 0] 0]) myvar # use myvar } 

Answer 3

Tcl does not support a static variable. Instead of using a global variable or a variable inside a namespace, another alternative is to implement your procedure as a method inside a class (see [Incr tcl] or snit). If you must implement a static variable, there is a page on the Tcl wiki that discusses this problem: http://wiki.tcl.tk/1532

Answer 4

Since I don't like global variables (unless you have a small script), I combine the solutions from @kostix and @Jackson:

 namespace eval foo { variable varList {} } proc foo::useCount {value} { variable varList lappend varList $value } foo::useCount One foo::useCount Two puts $foo::varList