Information Technology Reference
In-Depth Information
The Conditional Compilation Constructs
The
#if
and
#endif
directives are the matching demarcations of a conditional compilation
construct. Whenever there is an
#if
directive, there must also be a matching
#endif
.
The
#if
and
#if...#else
constructs are illustrated in Figure 22-1.
If the condition in the
#if
construct evaluates to
true
, the code section following it is
compiled. Otherwise, it is skipped.
In the
#if...#else
construct, if the condition evaluates to
true
,
CodeSection1
is com-
piled. Otherwise,
CodeSection2
is compiled.
Figure 22-1.
The #if and #else constructs
For example, the following code illustrates a simple
#if...#else
construct. If the symbol
RightHanded
is defined, the code between the
#if
and the
#else
will be compiled. Otherwise,
the code between the
#else
and the
#endif
will be compiled.
...
#if RightHanded
// Code implementing right-handed functionality
...
#else
// Code implementing left-handed functionality
...
#endif
