%------------------------------------------------------------------------------
% File     : SET006+4 : TPTP v7.2.0. Released v3.2.0.
% Domain   : Set Theory
% Axioms   : Ordinal numbers for the SET006+0 set theory axioms
% Version  : [Pas05] axioms.
% English  :

% Refs     : [Pas05] Pastre (2005), Email to G. Sutcliffe
% Source   : [Pas05]
% Names    :

% Status   : Satisfiable
% Syntax   : Number of formulae    :    8 (   0 unit)
%            Number of atoms       :   36 (   1 equality)
%            Maximal formula depth :   11 (   7 average)
%            Number of connectives :   29 (   1 ~  ;   1  |;  12  &)
%                                         (   7 <=>;   8 =>;   0 <=)
%                                         (   0 <~>;   0 ~|;   0 ~&)
%            Number of predicates  :    8 (   0 propositional; 1-3 arity)
%            Number of functors    :    6 (   2 constant; 0-3 arity)
%            Number of variables   :   28 (   0 singleton;  26 !;   2 ?)
%            Maximal term depth    :    3 (   1 average)
% SPC      : 

% Comments : Requires SET006+0.ax
%------------------------------------------------------------------------------
%---- Ordinal numbers and strict order relations
fof(ordinal_number,axiom,(
    ! [A] :
      ( member(A,on)
    <=> ( set(A)
        & strict_well_order(member_predicate,A)
        & ! [X] :
            ( member(X,A)
           => subset(X,A) ) ) ) )).

fof(strict_well_order,axiom,(
    ! [R,E] :
      ( strict_well_order(R,E)
    <=> ( strict_order(R,E)
        & ! [A] :
            ( ( subset(A,E)
              & ? [X] : member(X,A) )
           => ? [Y] : least(Y,R,A) ) ) ) )).

fof(least,axiom,(
    ! [R,E,M] :
      ( least(M,R,E)
    <=> ( member(M,E)
        & ! [X] :
            ( member(X,E)
           => ( M = X
              | apply(R,M,X) ) ) ) ) )).

fof(rel_member,axiom,(
    ! [X,Y] :
      ( apply(member_predicate,X,Y)
    <=> member(X,Y) ) )).

fof(strict_order,axiom,(
    ! [R,E] :
      ( strict_order(R,E)
    <=> ( ! [X,Y] :
            ( ( member(X,E)
              & member(Y,E) )
           => ~ ( apply(R,X,Y)
                & apply(R,Y,X) ) )
        & ! [X,Y,Z] :
            ( ( member(X,E)
              & member(Y,E)
              & member(Z,E) )
           => ( ( apply(R,X,Y)
                & apply(R,Y,Z) )
             => apply(R,X,Z) ) ) ) ) )).

fof(set_member,axiom,(
    ! [X] :
      ( set(X)
     => ! [Y] :
          ( member(Y,X)
         => set(Y) ) ) )).

fof(initial_segment,axiom,(
    ! [X,R,A,Y] :
      ( member(Y,initial_segment(X,R,A))
    <=> ( member(Y,A)
        & apply(R,Y,X) ) ) )).

fof(successor,axiom,(
    ! [A,X] :
      ( member(X,suc(A))
    <=> member(X,union(A,singleton(A))) ) )).

%------------------------------------------------------------------------------