SX/B Sub Question

Basic Jim

Hello,
·I am trying to understand SX/B a little better. I have writen basic programs and declared subs like "Runmotor····· Sub" And it works fine. When I look at examples written by experienced programers I see them use "Runmotor··· Sub··· 1,2" I don't see what the '1,2' means and why one would add that. The SX/B help file doesn't seem to explain this. Are these optional parms?

Thanks,
Jim W

JonnyMac

SUBs and FUNCs are covered in the Definitions section of the help file.

The reason for the number is that it tells the compiler how many (possible) bytes you can pass to the subroutine. In your question, the "1, 2" means that the subroutine expects at least one byte, but could handle two.

A good use for subroutines is to encapsulate SX/B keywords that generate a lot of code; PAUSE, for example. By putting PAUSE into a subroutine it only gets compiled once. By allowing variable parameters the subroutine can be as flexible as the original keyword. This subroutine handles PAUSE and will accept byte or word values.

' Use: DELAY ms
' -- 'ms' is delay in milliseconds, 1 - 65535

DELAY:
  IF __PARAMCNT = 1 THEN
    tmpW1 = __PARAM1                            ' save byte value
  ELSE
    tmpW1 = __WPARAM12                          ' save word value
  ENDIF
  PAUSE tmpW1 
  RETURN

Note that if your subroutine doesn't require any parameters you should specify zero.

Basic Jim

Thanks JonnMac,

The help file didn't explain it anywhere near as well as you did. I can see clearly now.

Best,
Jim W.

JonnyMac

That's my fault since I wrote the help file -- but it was a while ago and we always get better with age, right?

John Kauffman

Here is a section from the SX/B help "SX/B Definitions." An example follows in the help.


Subroutine Declaration

The programming and use of subroutines is simplified by declaring the subroutine name and the parameter(s) (if any) required. Additionally, the declaration of subroutines allows them to return a byte value (see FUNC, below, for return word values). Declaring subroutines offers significant advantages to the programmer:

The compiler can check code for the correct number of parameters
GOSUB is no longer required to call the subroutine
The subroutine can return a direct (byte) value
-- This is simpler than passing the variable's address (@someVar)
Code page management is automatically handled
SX/B subroutines are defined using the following syntax:

Label SUB {Min{, Max}}

Where Min is the minimum number of required parameters (if any) and Max is the maximum number of parameters passed to the subroutine. If Max is not specified then Min is the fixed number of parameters allowed.