ABL electronic PIC12 Personal Computer User Manual


 
Macros with Parameters
The following syntax is used to define a macro with parameters:
#define
macro_identifier
(
<arg_list>
)
token_sequence
Note there can be no whitespace between the
macro_identifier
and the “(”.
The optional
arg_list
is a sequence of identifiers separated by commas, not
unlike the argument list of a C function. Each comma-delimited identifier plays
the role of a formal argument or placeholder.
Such macros are called by writing
macro_identifier
(
<actual_arg_list>
)
in the subsequent source code. The syntax is identical to that of a function call;
indeed, many standard library C “functions” are implemented as macros.
However, there are some important semantic differences.
The optional
actual_arg_list
must contain the same number of comma-delim-
ited token sequences, known as actual arguments, as found in the formal
arg_list
of the #define line – there must be an actual argument for each for-
mal argument. An error will be reported if the number of arguments in the two
lists is different.
A macro call results in two sets of replacements. First, the macro identifier and the
parenthesis-enclosed arguments are replaced by the token sequence. Next, any for-
mal arguments occurring in the token sequence are replaced by the corresponding
real arguments appearing in the
actual_arg_list
. As with simple macro defini-
tions, rescanning occurs to detect any embedded macro identifiers eligible for
expansion.
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