Relational Operators
|
Operator |
Result |
Description |
|
== |
Equal |
Double equal sign |
|
!= |
Not equal |
exclamation point/equal sign |
|
< |
Less than |
left angle bracket |
|
<= |
Less than or equal |
left angle bracket/equal sign |
|
> |
Greater than |
right angle bracket |
|
>= |
Greater than or equal |
right angle bracket/equal sign |
All relational operations are unsigned. For example, the expression !0 > 4 is true since the complement of !0 is 1111 (assuming 4 bits of data), which is 15 in unsigned binary, and 15 is greater than 4. For the purpose of this example, a four-bit representation was assumed; in actual use, !0, the complement of 0, is 32 bits all set to 1.
Example
|
Expression |
Value |
|
2 == 3 |
False |
|
2 != 3 |
True |
|
3 < 5 |
True |
|
-1 > 2 |
True |
The logical values, true and false, are represented internally by numbers. Logical true is -1 in twos complement: all 32 bits are set to 1. Logical false is 0 in twos complement so all 32 bits are set to 0. This means that an expression producing a true or false value (a relational expression) can be used anywhere a number or numeric expression could be used and -1 or 0 will be substituted in the expression depending on the logical result.
For example, A = D $ (B == C); means that
A equals the complement of D if B equals C
A equals D if B does not equal C.
When using relational operators, always use parentheses to ensure the expression is evaluated in the order you expect. The logical operators & and # have a higher priority than the relational operators. The following equation
Select = [A15..A0] == ^hD000 # [A15..A0] ==<N>^h1000;
has the default parentheses grouping
Select = [A15..A0] == (^hD000 # [A15..A0]) ==<N>^h1000;
which is not the intended equation. To get the desired results, write the equation as follows:
Select = ([A15..A0] == ^hD000) # ([A15..A0] ==<N>^h1000);