Description |
 |
A conditional expression consists of three expressions. The
first and the second expressions are separated with a ?
character; the second and third expressions are separated with a
: character.
The first expression is evaluated. If the result is nonzero,
the second expression is evaluated and the result of the conditional
expression is the value of the second expression. If the first expression's
result is zero, the third expression is evaluated and the result
of the conditional expression is the value of third expression.
The first expression can have any scalar type. The second
and third expressions can be any of the following combinations:
Both arithmetic.
The usual arithmetic conversions are performed on the second
and third expressions. The resulting type of the conditional expression
is the result of the conversion.
Both are pointers to type T.
Arrays are converted to pointers, if necessary. The result
is a pointer to type T.
Identical type object.
The types can match and be structure, union, or void.
The result is that specific type.
Pointer and Null pointer constant or
a pointer to void
One expression may be a pointer (or array that is converted
to a pointer) and the other a null pointer constant or a pointer
to void. The result is the same type as the type of the pointer
operand.
In all cases, the result is not an lvalue.
Note that either the second or
the third expression is evaluated, but not both. Although not required
for readability, it is considered good programming style to enclose
the first expression in parentheses. For example:
min = (val1<val2) ? val1:val2; |
Example |
|
This expression returns x
if a is 0, or
return y if a
is not 0.
The following statement prints "I have 1 dog."
if num is equal
to 1, or "I have 3 dogs.",
if num is 3.
printf ("I have %d dog%s.\n",num, (num>1) ? "s" : ""); |
