reconsider R = {[0,1]} as non empty Relation ;
take
R
; R is complete
A1:
field R = {0,1}
by RELAT_1:17;
thus
R is confluent
REWRITE1:def 25 R is strongly-normalizing proof
let a,
b be
object ;
REWRITE1:def 22 ( a,b are_divergent_wrt R implies a,b are_convergent_wrt R )
given c being
object such that A2:
R reduces c,
a
and A3:
R reduces c,
b
;
REWRITE1:def 8 a,b are_convergent_wrt R
per cases
( a = b or a <> b )
;
suppose
a <> b
;
a,b are_convergent_wrt Rthen
(
a <> c or
b <> c )
;
then A4:
c in field R
by A2, A3, Th18;
then
a in {0,1}
by A1, A2, Th18;
then A5:
(
a = 0 or
a = 1 )
by TARSKI:def 2;
b in {0,1}
by A1, A3, A4, Th18;
then A6:
(
b = 0 or
b = 1 )
by TARSKI:def 2;
[0,1] in R
by TARSKI:def 1;
then A7:
R reduces 0 ,1
by Th15;
R reduces 1,1
by Th12;
hence
a,
b are_convergent_wrt R
by A5, A6, A7;
verum end; end;
end;
A8:
R is co-well_founded
proof
let Y be
set ;
REWRITE1:def 16 ( Y c= field R & Y <> {} implies ex a being object st
( a in Y & ( for b being object st b in Y & a <> b holds
not [a,b] in R ) ) )
assume that A9:
Y c= field R
and A10:
Y <> {}
;
ex a being object st
( a in Y & ( for b being object st b in Y & a <> b holds
not [a,b] in R ) )
reconsider Y9 =
Y as non
empty set by A10;
set y = the
Element of
Y9;
per cases
( 1 in Y or ( not 1 in Y & the Element of Y9 in Y ) )
;
suppose A12:
( not 1
in Y & the
Element of
Y9 in Y )
;
ex a being object st
( a in Y & ( for b being object st b in Y & a <> b holds
not [a,b] in R ) )take
0
;
( 0 in Y & ( for b being object st b in Y & 0 <> b holds
not [0,b] in R ) )thus
0 in Y
by A1, A9, A12, TARSKI:def 2;
for b being object st b in Y & 0 <> b holds
not [0,b] in Rlet b be
object ;
( b in Y & 0 <> b implies not [0,b] in R )assume
b in Y
;
( not 0 <> b or not [0,b] in R )hence
( not
0 <> b or not
[0,b] in R )
by A1, A9, A12, TARSKI:def 2;
verum end; end;
end;
R is irreflexive
hence
R is strongly-normalizing
by A8; verum