6.1 #define
Syntax:
#define name [value]#define name(arg, ...) [value]
Description:
Define a preprocessor macro. There are two forms of macros; (1) object-like macros that basically define a constant, and (2) function-like macros that do parameter substitution.
value may be any string, it
is not evaluated until the macro is expanded (used). If value is not
specified, it is set to 1.
Form (1) macros may be defined from the command line, using the
-D argument.
When form (2) is used, the macro must be called with the same number
of arguments it is defined with. Any occurrences of arg in
value will be replaced with the corresponding arg when
the macro is called. Note that the left parenthesis must appear immediately after
name (no spaces between), otherwise it will be interpreted as part of
the value of a form (1) macro.
Examples
Note that the placement of the first '(' is very significant in the examples below.
-
#define EIGHT (1 << 3) -
#define SQR(X) ((X)*(X))