_NOT: boolean -> boolean
The unary boolean operator "not" realises logical negation. not x is FALSE if x is TRUE, TRUE otherwise.
In expressions, "not" binds stronger than "and", but weaker than equality and relational operators.
> not TRUE
> not FALSE
> not 1=0
> not TRUE=FALSE
See also: Operator "and" (_AND), Operator "or" (_OR), Operators and Expressions.