Negation is the process of reversing the meaning of a Boolean expression. There are two approaches used to negate a Boolean expression.
First Approach
The first approach is the easiest one. Just use a NOT operator in front of the original Boolean expression and your negated Boolean expression is ready! For example,
PHP
if the original Boolean expression is $x > 5 && $y == 3
,
the negated Boolean expression becomes !($x > 5 && $y == 3)
.
Notice: Please note that the entire expression must be enclosed in parentheses. It would be completely incorrect if you had written the expression without parentheses, as
!$x > 5 && $y == 3
. In this case the NOT operator would negate only the first Boolean expression,$x > 5
.
Java, C++, C#
if the original Boolean expression is x > 5 && y == 3
,
the negated Boolean expression becomes !(x > 5 && y == 3)
.
Notice: Please note that the entire expression must be enclosed in parentheses. It would be completely incorrect if you had written the expression without parentheses, as
!x > 5 && y == 3
. In this case the NOT operator would negate only the first Boolean expression,x > 5
.
Visual Basic
if the original Boolean expression is x > 5 And y = 3
,
the negated Boolean expression becomes Not (x > 5 And y = 3)
.
Notice: Please note that the entire expression must be enclosed in parentheses. It would be completely incorrect if you had written the expression without parentheses, as Not
x > 5 And y = 3
. In this case the NOT operator would negate only the first Boolean expression,x > 5
.
Python
if the original Boolean expression is x > 5 and y == 3
,
the negated Boolean expression becomes not (x > 5 and y == 3)
.
Notice: Please note that the entire expression must be enclosed in parentheses. It would be completely incorrect if you had written the expression without parentheses, as not
x > 5 and y == 3
. In this case the NOT operator would negate only the first Boolean expression,x > 5
.
Second Approach
The second approach is a little bit more complex but not difficult to learn. All you must do is negate every operator according to the following table.
PHP
Original Operator |
Negated Operator |
== |
!= |
!= |
== |
> |
<= |
< |
>= |
<= |
> |
>= |
< |
&& |
|| |
|| |
&& |
! |
! |
Notice: Please note that the NOT operator ( ! ) remains intact.
For example,
if the original Boolean expression is $x > 5 && $y == 3
,
the negated Boolean expression becomes $x <= 5 || $y != 3
.
Java, C++, C#
Original Operator |
Negated Operator |
== |
!= |
!= |
== |
> |
<= |
< |
>= |
<= |
> |
>= |
< |
&& |
|| |
|| |
&& |
! |
! |
Notice: Please note that the NOT operator ( ! ) remains intact.
For example,
if the original Boolean expression is x > 5 && y == 3
,
the negated Boolean expression becomes x <= 5 || y != 3
.
Visual Basic
Original Operator |
Negated Operator |
= |
<> |
<> |
= |
> |
<= |
< |
>= |
<= |
> |
>= |
< |
And |
Or |
Or |
And |
Not |
Not |
Notice: Please note that the
Not
operator remains intact.
For example,
if the original Boolean expression is x > 5 And y = 3
,
the negated Boolean expression becomes x <= 5 And y <> 3
.
Python
Original Operator |
Negated Operator |
== |
!= |
!= |
== |
> |
<= |
< |
>= |
<= |
> |
>= |
< |
in |
not in |
not in |
in |
and |
or |
or |
and |
not |
not |
Notice: Please note that the
not
operator remains intact.
For example,
if the original Boolean expression is x > 5 and y == 3
,
the negated Boolean expression becomes x <= 5 or y != 3
.