ABL electronic PIC Microcontrollers PIC18 ユーザーズマニュアル

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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