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'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" RCS: @(#) $Id: return.n,v 1.3.18.1 2004/10/27 14:23:58 dkf Exp $
'\"
.so man.macros
.TH return n 7.0 Tcl "Tcl Built-In Commands"
.BS
'\" Note: do not modify the .SH NAME line immediately below!
.SH NAME
return \- Return from a procedure
.SH SYNOPSIS
\fBreturn \fR?\fB\-code \fIcode\fR? ?\fB\-errorinfo \fIinfo\fR? ?\fB\-errorcode\fI code\fR? ?\fIstring\fR?
.BE
.SH DESCRIPTION
.PP
Return immediately from the current procedure
(or top-level command or \fBsource\fR command),
with \fIstring\fR as the return value. If \fIstring\fR is not specified then
an empty string will be returned as result.
.SH "EXCEPTIONAL RETURN CODES"
.PP
In addition to the result of a procedure, the return
code of a procedure may also be set by \fBreturn\fR
through use of the \fB-code\fR option.
In the usual case where the \fB\-code\fR option isn't
specified the procedure will return normally.
However, the \fB\-code\fR option may be used to generate an
exceptional return from the procedure.
\fICode\fR may have any of the following values:
.TP 13
\fBok (or 0)\fR
Normal return: same as if the option is omitted. The return code
of the procedure is 0 (\fBTCL_OK\fR).
.TP 13
\fBerror (1)\fR
Error return: the return code of the procedure is 1 (\fBTCL_ERROR\fR).
The procedure command behaves in its calling context as if it
were the command \fBerror \fIresult\fR. See below for additional
options.
.TP 13
\fBreturn (2)\fR
The return code of the procedure is 2 (\fBTCL_RETURN\fR). The
procedure command behaves in its calling context as if it
were the command \fBreturn\fR (with no arguments).
.TP 13
\fBbreak (3)\fR
The return code of the procedure is 3 (\fBTCL_BREAK\fR). The
procedure command behaves in its calling context as if it
were the command \fBbreak\fR.
.TP 13
\fBcontinue (4)\fR
The return code of the procedure is 4 (\fBTCL_CONTINUE\fR). The
procedure command behaves in its calling context as if it
were the command \fBcontinue\fR.
.TP 13
\fIvalue\fR
\fIValue\fR must be an integer; it will be returned as the
return code for the current procedure.
.LP
The \fB\-code\fR option is rarely used.
It is provided so that procedures that implement
new control structures can reflect exceptional conditions back to
their callers.
.PP
Two additional options, \fB\-errorinfo\fR and \fB\-errorcode\fR,
may be used to provide additional information during error
returns.
These options are ignored unless \fIcode\fR is \fBerror\fR.
.PP
The \fB\-errorinfo\fR option specifies an initial stack
trace for the \fBerrorInfo\fR variable; if it is not specified then
the stack trace left in \fBerrorInfo\fR will include the call to
the procedure and higher levels on the stack but it will not include
any information about the context of the error within the procedure.
Typically the \fIinfo\fR value is supplied from the value left
in \fBerrorInfo\fR after a \fBcatch\fR command trapped an error within
the procedure.
.PP
If the \fB\-errorcode\fR option is specified then \fIcode\fR provides
a value for the \fBerrorCode\fR variable.
If the option is not specified then \fBerrorCode\fR will
default to \fBNONE\fR.
.SH EXAMPLES
First, a simple example of using \fBreturn\fR to return from a
procedure, interrupting the procedure body.
.CS
proc printOneLine {} {
puts "line 1" ;# This line will be printed.
\fBreturn\fR
puts "line 2" ;# This line will not be printed.
}
.CE
.PP
Next, an example of using \fBreturn\fR to set the value
returned by the procedure.
.CS
proc returnX {} {\fBreturn\fR X}
puts [returnX] ;# prints "X"
.CE
.PP
Next, a more complete example, using \fBreturn -code error\fR
to report invalid arguments.
.CS
proc factorial {n} {
if {![string is integer $n] || ($n < 0)} {
\fBreturn\fR -code error \\
"expected non-negative integer,\\
but got \\"$n\\""
}
if {$n < 2} {
\fBreturn\fR 1
}
set m [expr {$n - 1}]
set code [catch {factorial $m} factor]
if {$code != 0} {
\fBreturn\fR -code $code $factor
}
set product [expr {$n * $factor}]
if {$product < 0} {
\fBreturn\fR -code error \\
"overflow computing factorial of $n"
}
\fBreturn\fR $product
}
.CE
.PP
Next, a procedure replacement for \fBbreak\fR.
.CS
proc myBreak {} {
\fBreturn\fR -code break
}
.CE
.SH "SEE ALSO"
break(n), catch(n), continue(n), error(n), proc(n), source(n), tclvars(n)
.SH KEYWORDS
break, catch, continue, error, procedure, return
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