Blind" Parameters - HP 9835A Programming Manual

112
Communication Between BASIC and Assembly Language
"Blind" Parameters
With explicit parameter declarations, an error occurs if a different type of variable or expression
is passed. In many cases, the error is desirable - you do not want different types of arguments
corresponding to a single parameter declaration. But in other cases, the error might not be as
desirable. Take the example of a sort. You might want the sort to have the capability of sorting
any type of array. You have two choices in that case - you can make different routines, each
with the appropriate declarations, or you can use a single entry point and the ANY parameter
declaration.
The ANY declaration -
is "blind" to the type of the corresponding argument in the ICALL statement. When used, it
accepts any type of argument as valid - string, full-precision, short-precision, integer, file
number, array. The descriptor for the argument is stored in the three words set aside, just as in
the other declarations.
Now, if your entry looks like -
ISCD~:E
SUB
ISOURCE ANY
IS(DRCE REl
"!"
:"!
i
~.(.
r
::;C)("t:;
L..Ilfi
then any of the following calls would be valid -
~HLL Srn~t(Test$(*), 100)
I
r' :
~::li!
::; c:t-·
t
<
'r
i::':;:. t ::: .~:. ::::: :t i?
ij
::=
ICAll
SQrt(#l,l~~)
When using the ANY declaration, it becomes the responsibility of your assembly language
routine to determine what is a valid parameter and what is not. You lose the automatic type-
checking available with explicit declarations. Techniques for doing this are discussed in the
next section.