Initial revision

1 files changed, 80 insertions, 0 deletions

diff --git a/doc/uplevel.n b/doc/uplevel.n
new file mode 100644
index 0000000..0332ca1
--- /dev/null
+++ b/doc/uplevel.n
@@ -0,0 +1,80 @@
+'\"
+'\" Copyright (c) 1993 The Regents of the University of California.
+'\" Copyright (c) 1994-1997 Sun Microsystems, Inc.
+'\"
+'\" See the file "license.terms" for information on usage and redistribution
+'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
+'\" 
+'\" SCCS: @(#) uplevel.n 1.8 97/08/13 13:41:36
+'\" 
+.so man.macros
+.TH uplevel n "" Tcl "Tcl Built-In Commands"
+.BS
+'\" Note:  do not modify the .SH NAME line immediately below!
+.SH NAME
+uplevel \- Execute a script in a different stack frame
+.SH SYNOPSIS
+\fBuplevel \fR?\fIlevel\fR?\fI arg \fR?\fIarg ...\fR?
+.BE
+
+.SH DESCRIPTION
+.PP
+All of the \fIarg\fR arguments are concatenated as if they had
+been passed to \fBconcat\fR; the result is then evaluated in the
+variable context indicated by \fIlevel\fR.  \fBUplevel\fR returns
+the result of that evaluation.
+.PP
+If \fIlevel\fR is an integer then
+it gives a distance (up the procedure calling stack) to move before
+executing the command.  If \fIlevel\fR consists of \fB#\fR followed by
+a number then the number gives an absolute level number.  If \fIlevel\fR
+is omitted then it defaults to \fB1\fR.  \fILevel\fR cannot be
+defaulted if the first \fIcommand\fR argument starts with a digit or \fB#\fR.
+.PP
+For example, suppose that procedure \fBa\fR was invoked
+from top-level, and that it called \fBb\fR, and that \fBb\fR called \fBc\fR.
+Suppose that \fBc\fR invokes the \fBuplevel\fR command.  If \fIlevel\fR
+is \fB1\fR or \fB#2\fR  or omitted, then the command will be executed
+in the variable context of \fBb\fR.  If \fIlevel\fR is \fB2\fR or \fB#1\fR
+then the command will be executed in the variable context of \fBa\fR.
+If \fIlevel\fR is \fB3\fR or \fB#0\fR then the command will be executed
+at top-level (only global variables will be visible).
+.PP
+The \fBuplevel\fR command causes the invoking procedure to disappear
+from the procedure calling stack while the command is being executed.
+In the above example, suppose \fBc\fR invokes the command
+.CS
+\fBuplevel 1 {set x 43; d}\fR
+.CE
+where \fBd\fR is another Tcl procedure.  The \fBset\fR command will
+modify the variable \fBx\fR in \fBb\fR's context, and \fBd\fR will execute
+at level 3, as if called from \fBb\fR.  If it in turn executes
+the command
+.CS
+\fBuplevel {set x 42}\fR
+.CE
+then the \fBset\fR command will modify the same variable \fBx\fR in \fBb\fR's
+context:  the procedure \fBc\fR does not appear to be on the call stack
+when \fBd\fR is executing.  The command ``\fBinfo level\fR'' may
+be used to obtain the level of the current procedure.
+.PP
+\fBUplevel\fR makes it possible to implement new control
+constructs as Tcl procedures (for example, \fBuplevel\fR could
+be used to implement the \fBwhile\fR construct as a Tcl procedure).
+.PP
+\fBnamespace eval\fR 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 \fBnamespace eval\fR command
+counts as another call level for \fBuplevel\fR and \fBupvar\fR commands.
+For example, \fBinfo level 1\fR will return a list
+describing a command that is either
+the outermost procedure call or the outermost \fBnamespace eval\fR command.
+Also, \fBuplevel #0\fR evaluates a script
+at top-level in the outermost namespace (the global namespace).
+
+.SH "SEE ALSO"
+namespace(n)
+
+.SH KEYWORDS
+context, level, namespace, stack frame, variables