## TPTP Problem File: ROB025-1.p

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```%--------------------------------------------------------------------------
% File     : ROB025-1 : TPTP v7.5.0. Released v1.0.0.
% Domain   : Robbins Algebra
% Problem  : -(X + Y) = intersection(-X,-Y) => Boolean
% Version  : [Win90] (equality) axioms : Incomplete.
% English  : If for all X and Y, -(X + Y) = intersection(-X,-Y) then the
%            algebra is Boolean.

% Refs     : [Win90] Winker (1990), Robbins Algebra: Conditions that make a
%          : [WW+90] Wos et al. (1990), Automated Reasoning Contributes to
% Source   : [WW+90]
% Names    : RA-2 [WW+90]

% Status   : Unsatisfiable
% Rating   : 1.00 v2.0.0
% Syntax   : Number of clauses     :   11 (   0 non-Horn;   6 unit;   4 RR)
%            Number of atoms       :   17 (   0 equality)
%            Maximal clause size   :    3 (   2 average)
%            Number of predicates  :    1 (   0 propositional; 2-2 arity)
%            Number of functors    :    5 (   2 constant; 0-2 arity)
%            Number of variables   :   23 (   0 singleton)
%            Maximal term depth    :    6 (   2 average)
% SPC      : CNF_UNS_RFO_NEQ_HRN

% Comments : Commutativity, associativity, and Huntington's axiom
%            axiomatize Boolean algebra.
%          : Intersection is not defined, so this problem may be broken.
%--------------------------------------------------------------------------
%----Include axioms for Robbins algebra
%include('Axioms/ROB001-0.ax').
%--------------------------------------------------------------------------
cnf(reflexivity,axiom,
( equalish(X,X) )).

cnf(symmetry,axiom,
( ~ equalish(X,Y)
| equalish(Y,X) )).

cnf(transitivity,axiom,
( ~ equalish(X,Y)
| ~ equalish(Y,Z)
| equalish(X,Z) )).

( ~ equalish(A,B)

( ~ equalish(D,E)

cnf(inverse_substitution1,axiom,
( ~ equalish(G,H)
| equalish(negate(G),negate(H)) )).