12.5.33    return

Description:   Return from a procedure

Syntax:         return ?-code code? ?-errorinfo info? ?-errorcode code? ?string?

         

Argument:     code, errorcodes, user assigned value

Returns:        return value is the value specified in a return command

See Also:       proc, break, continue

 

Examples:     

   proc power {base p} {

    set result 1

    while {$p > 0} {

        set result [expr $result * $base]

        set p [expr $p - 1]

    }

    return $result

}

 

SETVAL tag1=[power 2 6]

SETVAL answr=[power [GETVAL basetag] [GETVAL pwrtag]]

SETVAL answr2=[power [GETVAL basetag2] [GETVAL pwrtag2]]

 

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 returns

In the usual case where the -code option isn’t specified the procedure will return normally (its completion code will be TCL_OK). However, the -code option may be used to generate an exceptional return from the procedure. Code may have any of the following values:

 

ok                    Normal return: same as if the option is omitted.

error               Error return: same as if the error command were used to terminate the procedure, except for handling of errorInfo and errorCode variables (see below).

return             The current procedure will return with a completion code of TCL_RETURN, so that the procedure that invoked it will return also.

break              The current procedure will return with a completion code of TCL_BREAK, which will terminate the innermost nested loop in the code that invoked the current procedure.

continue        The current procedure will return with a completion code of TCL_CONTINUE, which will terminate the current iteration of the innermost nested loop in the code that invoked the current procedure.

 

value           Value must be an integer; it will be returned as the completion 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.