Download System 8813 Macro Assembler - PolyMorphic

MACRO-8S Assembler Manual
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polyMorphic Systems
merely counts them and returns their total number.
In other
words, if the same string given to LEN[] is substituted into a
DB pop in the operand field, the outputted object code will occupy the number of bytes in memory that LEN[] returns as its
value.
As an example, consider th& following:
DB
LEN['Hi there!']+2,
'Hi there!',CR,LF
This statement will assemble first a byte with value 11 (decimal),
then 9 bytes of ASCII character information followed by 2 symbolically defined constants.
2.2.1.5.2
NULL(]
In a macro, it is possible to pass a parameter which contains
no characters at all. This happens when a position in the operand field of the macro invocation is left empty. The parameter
is then considered non-existent or "null." The NULL[] function
allows a macro to take appropriate action when an optional parameter has been omitted.
It returns a logical value of TRUE
(-lor 0FFFF hex) when there is a null parameter between the
brackets and FALSE (0) when any number of valid parameters can
be found there.
Example:
DW
NULL['I am not nullt],NULL[]
This assembles a 0000H followed by a 0FFFH.
Example of use inside a macro:
MAYBE
MACRO
IF
DW
ENDIF
ENDM
NOT NULL [ #: 1]
#1
i I f there's a parameter #1,
jthen assemble it.
Thus the invocation
MAYBE
5
expands into
OW
5
But with a null operand field, MAYBE assembles nothing.
2.2.1.6
Mathematical expressions
It was said above, in the discussion on numbers, symbols, the
dollar sign, and short strings, that each of these things is a