Optional arguments
can be useful when there are some situations where you want the macro to take a
default action rather than accepting a value.
In fact it will save code in the final assembled program since, by not
providing an argument, the code which loads the argument doesn’t have to be
implemented in that instance.
An example of a
macro generated using optional arguments and built using the wizard is shown in
Enhanced Alpha
Clear Screen.
Optional Return
parameters could be used for Macros which perform a function which does not
require a return value – e.g. AddParam (Param),
Status might add a parameter
into an array if the array had space and the value wasn’t already in the
array. The return parameter could be
used to return the status of the function e.g. 0 for OK, 1 for Array Full, 2
for Already there etc…. If the calling
routine didn’t need to know whether the function succeeded it could leave out
the return part of the syntax.
Note – for Macros that return a parameter there may be restrictions on the use of an optional return parameter. When using the “last parameter” method as the return value (Return dropdown set to “Last Param”) you are permitted the following:
Mandatory arguments and a mandatory return
Optional arguments and a mandatory return
Mandatory arguments and an optional return
This restriction does not apply to the Inline method.