[Richard Suchenwirth] 2006-02-07 - For doing some OO sugar, I needed a way that [interp alias]es are cleaned up when the proc scope where they were defined is left. Here's my solution with a guard variable, to which an unset [trace] is tied:

 proc alias {name = args} {
   upvar 1 __$name __$name
   eval [list interp alias {} $name {}] $args
   set __$name ""
   trace var __$name u "interp alias {} $name {} ;#"
 }

 proc test {} {
   alias up = string toupper
   return [up hello],[up world]
 }
 146 % test
 HELLO,WORLD
 277 % up this
 invalid command name "up"
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[NEM] cautions though that the scope of aliases aren't really proc local, e.g.:

 % proc test2 {} {
     alias up = string toupper
     return [test],[up more]
 }
 % test2
 invalid command name "up"

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[RS] Right. I should better have said "short-lived". But in my use case, accidentally reusing a name is less of a concern - it will be unambiguous handles to objects, for the popular
 $obj method arg arg...
style. My worry was that the alias table would run full, if 10,000s of such were created every hour...

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[Category Development]