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OpenDarwin 7.2.1 - man page for uplevel (opendarwin section n)

uplevel(n)			      Tcl Built-In Commands			       uplevel(n)


       uplevel - Execute a script in a different stack frame

       uplevel ?level? arg ?arg ...?

       All of the arg arguments are concatenated as if they had been passed to concat; the result
       is then evaluated in the variable context indicated by level.  Uplevel returns the  result
       of that evaluation.

       If  level  is an integer then it gives a distance (up the procedure calling stack) to move
       before executing the command.  If level consists of # followed by a number then the number
       gives  an absolute level number.  If level is omitted then it defaults to 1.  Level cannot
       be defaulted if the first command argument starts with a digit or #.

       For example, suppose that procedure a was invoked from top-level, and that  it  called  b,
       and that b called c.  Suppose that c invokes the uplevel command.  If level is 1 or #2  or
       omitted, then the command will be executed in the variable context of b.  If level is 2 or
       #1  then  the  command will be executed in the variable context of a.  If level is 3 or #0
       then the command will be executed at top-level (only global variables will be visible).

       The uplevel command causes the invoking procedure to disappear from the procedure  calling
       stack  while  the  command is being executed.  In the above example, suppose c invokes the
	      uplevel 1 {set x 43; d}
       where d is another Tcl procedure.  The set command will modify the variable x in b's  con-
       text, and d will execute at level 3, as if called from b.  If it in turn executes the com-
	      uplevel {set x 42}
       then the set command will modify the same variable x in b's context:  the procedure c does
       not appear to be on the call stack when d is executing.	The command ``info level'' may be
       used to obtain the level of the current procedure.

       Uplevel makes it possible to implement new control constructs as Tcl procedures (for exam-
       ple, uplevel could be used to implement the while construct as a Tcl procedure).

       namespace  eval	is  another way (besides procedure calls) that the Tcl naming context can
       change.	It adds a call frame to the stack to represent the namespace context.  This means
       each  namespace	eval command counts as another call level for uplevel and upvar commands.
       For example, info level 1 will return a list describing a command that is either the  out-
       ermost procedure call or the outermost namespace eval command.  Also, uplevel #0 evaluates
       a script at top-level in the outermost namespace (the global namespace).

       namespace(n), upvar(n)

       context, level, namespace, stack frame, variables

Tcl										       uplevel(n)

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