[Zarutian] tormented [kbk] the other day (late Desember 2007 or early January 2008) with this:

 package Tcl 8.5
 variable storage {}
 proc restore {caller vars} {
   if {![dict exists $::storage $caller]} { return }
   foreach var $vars {
     uplevel 1 [list set $var [dict get $::storage $caller $var]]
   }
 }
 proc save {caller vars} {
   foreach var $vars {
     dict set ::storage $caller $var [uplevel 1 [list set $var]]
   }
 }
 
 proc persist {args} {
   set vars $args; unset args
   if {[uplevel 1 [list info exists __[info level 0]]]} { return }
   uplevel 1 [list set __[info level 0] exists]

   set caller [lindex [info level 1]]
   uplevel 1 [list restore $caller $vars]
   catch [list uplevel 1 [info body $caller]] result options
   uplevel 1 [list save $caller $vars]
   dict incr options -level +2
   return -options $options $result 
 }
 
 proc prufa {args} {
   persist si
   incr si 42
   puts "si = $si"
 }

another well known [proc]edure decorator is [memoize], but that only works for referentially transparent functions (i.e. side-effect free procedures).

[DKF]: So what does this code ''do''? It's not at all clear from just reading the code...

[RS]: Could it have to do with [static variables]? But I don't understand the code either...

[Zarutian]: indeed the above example of an decorator is for persisting [static variables].
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