|Syntax||END DEFine [name]|
This command marks the end of the DEFine PROCedure and DEFine FuNction SuperBASIC structures, and has no meaning on its own. You may if you wish, place the name of the PROCedure or FuNction after END DEFine to help make the SuperBASIC program more readable - this will however have no effect on how the command is treated by the interpreter, which will still take the next END DEFine as the end of the current definition block (even if it is followed by a different name).
The interpreter will jump out of a definition block whenever it meets a RETurn statement. It will also jump out of a DEFine PROCedure definition when it meets an END DEFine statement. This does of course mean that END DEFine can be used in the middle of a PROCedure to force a return to the calling statement - however, this can cause other problems and a RETurn should be used, with END DEFine only appearing at the very end of the definition block.
On the other hand, the interpreter can only jump out of a DEFine FuNction definition if it meets a RETurn - if the interpreter comes across an END DEFine in such situations, it will report the error ‘Error In Expression’. On SMS the error ‘RETurn not in Procedure or Function’ is reported. If the definition block is not actually being used, but the interpreter is working its way through the program, when a DEFine PROCedure or DEFine FuNction statement is met, the interpreter will search for the next END DEFine, and having found one, will resume the program at the next statement.
This does however mean, that unless an in-line DEFine structure is being used, if this command is missing, the interpreter will carry on searching through the program and may just stop without an error if END DEFine does not appear anywhere in the program after the initial DEFine PROCedure (or DEFine FuNction).
The above rules mean that the following example will work under SuperBASIC, but is extremely inefficient and difficult to decode:
10 FOR i=1 TO 100 20 PRINT power(i) 30 DEFine FuNction power(x) 40 RETurn 2^x 50 END DEFine 60 END FOR i
See if you can work out why the following program goes wrong:
100 FOR i=1 TO 100 110 PRINT power(i) 120 DEFine FuNction power(x) 130 DEFine FuNction base 140 RETurn 2 150 END DEFine base 160 RETurn base^x 170 END DEFine power 180 END FOR i
If you are having trouble, try inserting:
155 PRINT 'Program line 155:';x
END DEFine need not appear in an in-line definition statement, except under SMS.
Checks are made on a program before it is run, and so if an END DEFine statement is missing, this will be reported as an error (‘Incomplete DEFine clause’). SMS’s improved interpreter will report the error ‘Misplaced END DEFine’ if END DEFine does not mark the end of a DEFine PROCedure or DEFine FuNction block.