The Boolean NOT 'NOT' operator returns TRUE (-1) if the operand is FALSE (0), or returns FALSE (0) if the operand is TRUE (non-zero). Boolean NOT can be used in both variable and constant expressions. Example:
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X := NOT Y |
The above example returns the Boolean opposite of Y; TRUE (-1) if Y is zero, or FALSE (0) if Y is non-zero. During the comparison, it promotes the value of Y to -1 if it is non-zero, making any value, other than 0, a -1, so that the comparison becomes: "If NOT true" or "If NOT false"
Quite often this operator is used in combination with other comparison operators, such as in the following example.
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