uplevel(n)                   Tcl ( )                   uplevel(n)



     _________________________________________________________________

     NAME
          uplevel - Execute a script in a different stack frame

     SYNOPSIS
          uplevel ?level? arg ?arg ...?
     _________________________________________________________________


     DESCRIPTION
          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 command

               uplevel 1 {set x 43; d}
          where d is another Tcl  procedure.   The  set  command  will
          modify  the variable x in b's context, and d will execute at
          level 3, as if called from b.  If it in  turn  executes  the
          command

               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 example, uplevel could be



     Page 1                                         (printed 11/11/93)






     uplevel(n)                   Tcl ( )                   uplevel(n)



          used to implement the while construct as a Tcl procedure).


     KEYWORDS
          context, stack frame, variables


















































     Page 2                                         (printed 11/11/93)