PLOGHELP NOT                                  Chris Mellish, August 1982
                                Revised by Kathryn Seifert  October 1986

Operator and predicate which invert success and failure

    ?- not(X).
    ?- \+ X.

Keywords: negation, success, failure, operators, symbols,


A goal that succeeds if and only if X fails.  For those that like
symbols, there is the operator "\+", which is exactly the same as "not",
but it is also declared as a prefix operator, of precedence 249. (See
PLOGHELP * OP). (Note that neither "not" nor "\+" will work with
modules.).

Some predicates, such as "var" have a matching predicate ("nonvar")
which could have been defined as
    nonvar(X) :- not(var(X)).

The operators = == and =:= have "negated" predicates, see HELP * EQUAL.

-- RELATED DOCUMENTATION ----------------------------------------------

PLOGHELP * SYMBOLS
 Summary and index of HELP files for symbols used in Prolog

PLOGHELP * OPERATORS
 Operator declarations made when the Prolog system is loaded

PLOGHELP * OP
 How to declare operators