if statement can be used to
compute absolute value:
if ( value < 0 ) abs = -value; else abs = value;
This is awkward for such a simple idea. The following does the same thing in one statement:
abs = (value < 0 ) ? -value : value ;
This statement uses a conditional operator.
The right side of the = is a conditional expression.
The expression is evalutated to produce a value,
which is then assigned to the variable,
true-or-false-condition ? value-if-true : value-if-false
It works like this:
Here is how it works with the above example:
double value = -34.569; double abs; abs = (value < 0 ) ? -value : value ; ------------- ------ 1. condition 2. this is evaluated, is true to +34.569 ---- 3. The +34.569 is assigned to abs
The conditional expression is a type of expression--that is, it asks for
a value to be computed but does not by itself change any variable.
In the above example, the variable
value is not changed.