C Programming Absolute Beginner's Guide (3rd Edition)

If the test in the first set of parentheses is true, the trueStatement executes. If the test in the first
set of parentheses is false, the falseStatement executes. The conditional operator you just saw
does exactly the same thing as this if...else statement:

if (total <= 3850.0

{ total *= 1.10; }

else

{ total *= 1.05; )

This statement tells C to multiply total by 1.10 or by 1.05, depending on the result of the relational
test.

Just about any if...else statement can be rewritten as a conditional statement. The conditional
requires less typing, you won’t accidentally leave off a brace somewhere, and the conditional runs
more efficiently than an if...else because it compiles into more compact code.

Tip

The format of the conditional operator is obvious when you think of it like this: The

question mark asks a question. Keeping this in mind, you could state the earlier

example as follows: Is the total <= 3850.0? If so, do the first thing; otherwise, do

the second.

C programmers don’t like the redundancy you saw in the earlier use of the conditional operator. As
you can see, the total variable appears twice. Both times, it is being assigned a value. When you
face such a situation, take the assignment out of the conditional operator’s statements:

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total *= (total <= 3850.0)? (1.10): (1.05);

Don’t replace every single if...else with a conditional operator. Many times, if...else is
more readable, and some conditional statements are just too complex to squeeze easily into a
conditional operator. However, when a simple if...else is all that’s needed, the conditional
operator provides a nice alternative.

The conditional operator offers one additional advantage over if: The conditional often can appear
in places where if can’t go. The following print(f) prints a trailing s if the number of pears is
more than 1:

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printf("I ate %d pear%s\n", numPear, (numPear>1)? ("s.") : ("."));

If the value in numPear is greater than 1 , you’ll see something like this printed:

I ate 4 pears.

But if there is only one pear, you’ll see this:

I ate 1 pear.