return(n)

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NAME

       return - Return from a procedure

SYNOPSIS

       return ?-code code? ?-errorinfo info? ?-errorcode code? ?string?
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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 proce-
       dure 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 fol-
       lowing 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  condi-
       tions back to their callers.

       Two  additional options, -errorinfo and -errorcode, may be used to pro-
       vide additional information during error returns.   These  options  are
       ignored unless code is error.

       The  -errorinfo  option specifies an initial stack trace for the error-
       Info 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  pro-
       cedure.
              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(n),  catch(n),   continue(n),   error(n),   proc(n),   source(n),
       tclvars(n)

KEYWORDS

       break, catch, continue, error, procedure, return

Tcl                                   7.0                            return(n)