HP 3000 Manuals HP 3000 Manuals
Conditional Operator
The conditional operator (?:) performs an if-then-else using three
expressions.
Syntax
conditional-expression ::=
logical-OR-expression
logical-OR-expression ? expression : conditional-expression
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:
1. 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.
2. Both are pointers to type T.
Arrays are converted to pointers, if necessary. The result
is a pointer to type T.
3. Identical type object.
The types can match and be structure, union, or void. The
result is that specific type.
4. 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.
a == 0 ? x : y
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" : "");