Provided by: tcl8.4-doc_8.4.20-7_all 
NAME
return - Return from a procedure
SYNOPSIS
return ?-code code? ?-errorinfo info? ?-errorcode code? ?string? _________________________________________________________________
DESCRIPTION
Return immediately from the current procedure (or top-level command or source command), with string as
the return value. If string is not specified then an empty string will be returned as result.
EXCEPTIONAL RETURN CODES
In addition to the result of a procedure, the return code of a procedure may also be set by return
through use of the -code option. In the usual case where the -code option isn't specified the procedure
will return normally. However, the -code option may be used to generate an exceptional return from the
procedure. Code may have any of the following values:
ok (or 0) Normal return: same as if the option is omitted. The return code of the procedure is 0
(TCL_OK).
error (1) Error return: the return code of the procedure is 1 (TCL_ERROR). The procedure command
behaves in its calling context as if it were the command error result. See below for
additional options.
return (2) The return code of the procedure is 2 (TCL_RETURN). The procedure command behaves in its
calling context as if it were the command return (with no arguments).
break (3) The return code of the procedure is 3 (TCL_BREAK). The procedure command behaves in its
calling context as if it were the command break.
continue (4) The return code of the procedure is 4 (TCL_CONTINUE). The procedure command behaves in its
calling context as if it were the command continue.
value Value must be an integer; it will be returned as the return code for the current procedure.
The -code option is rarely used. It is provided so that procedures that implement new control structures
can reflect exceptional conditions back to their callers.
Two additional options, -errorinfo and -errorcode, may be used to provide additional information during
error returns. These options are ignored unless code is error.
The -errorinfo option specifies an initial stack trace for the errorInfo variable; if it is not
specified then the stack trace left in errorInfo 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 info value is supplied from the value left in errorInfo after a catch command trapped an
error within the procedure.
If the -errorcode option is specified then code provides a value for the errorCode variable. If the
option is not specified then errorCode will default to NONE.
EXAMPLES
First, a simple example of using return to return from a procedure, interrupting the procedure body.
proc printOneLine {} {
puts "line 1" ;# This line will be printed.
return
puts "line 2" ;# This line will not be printed.
}
Next, an example of using return to set the value returned by the procedure.
proc returnX {} {return X}
puts [returnX] ;# prints "X"
Next, a more complete example, using return -code error to report invalid arguments.
proc factorial {n} {
if {![string is integer $n] || ($n < 0)} {
return -code error \
"expected non-negative integer,\
but got \"$n\""
}
if {$n < 2} {
return 1
}
set m [expr {$n - 1}]
set code [catch {factorial $m} factor]
if {$code != 0} {
return -code $code $factor
}
set product [expr {$n * $factor}]
if {$product < 0} {
return -code error \
"overflow computing factorial of $n"
}
return $product
}
Next, a procedure replacement for break.
proc myBreak {} {
return -code break
}
SEE ALSO
break(3tcl), catch(3tcl), continue(3tcl), error(3tcl), proc(3tcl), source(3tcl), tclvars(3tcl)
KEYWORDS
break, catch, continue, error, procedure, return