A Boolean assertion is simply an expression that results in a true or false answer. For example,
are all statements that will result in a true or false answer.
To negate a Boolean assertion means to write the opposite of a given Boolean assertion. For example, given the following Boolean assertions noted as A, the corresponding negated statements are the result of applying the !
operator to A.
A |
!A |
|
|
5 == x |
5 != x |
x < 5 |
x >= 5 |
x >= 5 |
x < 5 |
Notice that negations of Boolean assertions can be used to re-write code. For example:
if (!(x < 5))
// do something...
can be rewritten as
if (x >= 5)
// do something ...
This is important because we understand positive statements much more easily than statements that contain one or more !s.