:: Subsets of Topological Spaces
:: by Miros{\l}aw Wysocki and Agata Darmochwa\l
::
:: Received April 28, 1989
:: Copyright (c) 1990 Association of Mizar Users


begin

theorem :: TOPS_1:1
canceled;

theorem :: TOPS_1:2
canceled;

theorem :: TOPS_1:3
canceled;

theorem :: TOPS_1:4
canceled;

theorem :: TOPS_1:5
canceled;

theorem :: TOPS_1:6
canceled;

theorem :: TOPS_1:7
canceled;

theorem :: TOPS_1:8
canceled;

theorem :: TOPS_1:9
canceled;

theorem :: TOPS_1:10
canceled;

theorem :: TOPS_1:11
canceled;

theorem :: TOPS_1:12
canceled;

theorem :: TOPS_1:13
canceled;

theorem :: TOPS_1:14
canceled;

theorem :: TOPS_1:15
canceled;

theorem :: TOPS_1:16
canceled;

theorem :: TOPS_1:17
canceled;

theorem :: TOPS_1:18
canceled;

theorem :: TOPS_1:19
canceled;

theorem :: TOPS_1:20
canceled;

theorem :: TOPS_1:21
for TS being 1-sorted
for K, Q being Subset of TS st K ` = Q ` holds
K = Q by SUBSET_1:64;

theorem :: TOPS_1:22
canceled;

theorem :: TOPS_1:23
canceled;

theorem :: TOPS_1:24
canceled;

theorem :: TOPS_1:25
canceled;

theorem :: TOPS_1:26
canceled;

theorem Th27: :: TOPS_1:27
for GX being TopStruct holds Cl ([#] GX) = [#] GX
proof end;

registration
let T be TopSpace;
let P be Subset of T;
cluster Cl P -> closed ;
coherence
Cl P is closed
proof end;
end;

theorem :: TOPS_1:28
canceled;

theorem Th29: :: TOPS_1:29
for GX being TopStruct
for R being Subset of GX holds
( R is closed iff R ` is open )
proof end;

registration
let T be TopSpace;
let R be closed Subset of T;
cluster R ` -> open ;
coherence
R ` is open by Th29;
end;

theorem Th30: :: TOPS_1:30
for GX being TopStruct
for R being Subset of GX holds
( R is open iff R ` is closed )
proof end;

registration
let T be TopSpace;
cluster open Element of K10( the carrier of T);
existence
ex b1 being Subset of T st b1 is open
proof end;
end;

registration
let T be TopSpace;
let R be open Subset of T;
cluster R ` -> closed ;
coherence
R ` is closed by Th30;
end;

theorem :: TOPS_1:31
for GX being TopStruct
for S, T being Subset of GX st S is closed & T c= S holds
Cl T c= S
proof end;

theorem Th32: :: TOPS_1:32
for TS being TopSpace
for K, L being Subset of TS holds (Cl K) \ (Cl L) c= Cl (K \ L)
proof end;

theorem :: TOPS_1:33
canceled;

theorem Th34: :: TOPS_1:34
for GX being TopStruct
for R, S being Subset of GX st R is closed & S is closed holds
Cl (R /\ S) = (Cl R) /\ (Cl S)
proof end;

registration
let TS be TopSpace;
let P, Q be closed Subset of TS;
cluster P /\ Q -> closed Subset of TS;
coherence
for b1 being Subset of TS st b1 = P /\ Q holds
b1 is closed
proof end;
cluster P \/ Q -> closed Subset of TS;
coherence
for b1 being Subset of TS st b1 = P \/ Q holds
b1 is closed
proof end;
end;

theorem :: TOPS_1:35
for TS being TopSpace
for P, Q being Subset of TS st P is closed & Q is closed holds
P /\ Q is closed ;

theorem :: TOPS_1:36
for TS being TopSpace
for P, Q being Subset of TS st P is closed & Q is closed holds
P \/ Q is closed ;

registration
let TS be TopSpace;
let P, Q be open Subset of TS;
cluster P /\ Q -> open Subset of TS;
coherence
for b1 being Subset of TS st b1 = P /\ Q holds
b1 is open
proof end;
cluster P \/ Q -> open Subset of TS;
coherence
for b1 being Subset of TS st b1 = P \/ Q holds
b1 is open
proof end;
end;

theorem :: TOPS_1:37
for TS being TopSpace
for P, Q being Subset of TS st P is open & Q is open holds
P \/ Q is open ;

theorem :: TOPS_1:38
for TS being TopSpace
for P, Q being Subset of TS st P is open & Q is open holds
P /\ Q is open ;

theorem Th39: :: TOPS_1:39
for GX being non empty TopSpace
for R being Subset of GX
for p being Point of GX holds
( p in Cl R iff for T being Subset of GX st T is open & p in T holds
R meets T )
proof end;

theorem Th40: :: TOPS_1:40
for TS being TopSpace
for Q, K being Subset of TS st Q is open holds
Q /\ (Cl K) c= Cl (Q /\ K)
proof end;

theorem :: TOPS_1:41
for TS being TopSpace
for Q, K being Subset of TS st Q is open holds
Cl (Q /\ (Cl K)) = Cl (Q /\ K)
proof end;

definition
let GX be TopStruct ;
let R be Subset of GX;
func Int R -> Subset of GX equals :: TOPS_1:def 1
(Cl (R `)) ` ;
coherence
(Cl (R `)) ` is Subset of GX ;
projectivity
for b1, b2 being Subset of GX st b1 = (Cl (b2 `)) ` holds
b1 = (Cl (b1 `)) ` ;
end;

:: deftheorem defines Int TOPS_1:def 1 :
for GX being TopStruct
for R being Subset of GX holds Int R = (Cl (R `)) ` ;

theorem :: TOPS_1:42
canceled;

theorem Th43: :: TOPS_1:43
for TS being TopSpace holds Int ([#] TS) = [#] TS
proof end;

theorem Th44: :: TOPS_1:44
for GX being TopStruct
for T being Subset of GX holds Int T c= T
proof end;

theorem :: TOPS_1:45
canceled;

theorem Th46: :: TOPS_1:46
for TS being TopSpace
for K, L being Subset of TS holds (Int K) /\ (Int L) = Int (K /\ L)
proof end;

registration
let GX be TopStruct ;
cluster Int ({} GX) -> empty ;
coherence
Int ({} GX) is empty
proof end;
end;

theorem :: TOPS_1:47
for GX being TopStruct holds Int ({} GX) = {} GX ;

theorem Th48: :: TOPS_1:48
for GX being TopStruct
for T, W being Subset of GX st T c= W holds
Int T c= Int W
proof end;

theorem Th49: :: TOPS_1:49
for GX being TopStruct
for T, W being Subset of GX holds (Int T) \/ (Int W) c= Int (T \/ W)
proof end;

theorem :: TOPS_1:50
for TS being TopSpace
for K, L being Subset of TS holds Int (K \ L) c= (Int K) \ (Int L)
proof end;

registration
let T be TopSpace;
let K be Subset of T;
cluster Int K -> open ;
coherence
Int K is open ;
end;

theorem :: TOPS_1:51
canceled;

theorem :: TOPS_1:52
canceled;

theorem :: TOPS_1:53
canceled;

registration
let T be TopSpace;
cluster empty -> open Element of K10( the carrier of T);
coherence
for b1 being Subset of T st b1 is empty holds
b1 is open
proof end;
cluster [#] T -> open ;
coherence
[#] T is open
proof end;
end;

registration
let T be TopSpace;
cluster open closed Element of K10( the carrier of T);
existence
ex b1 being Subset of T st
( b1 is open & b1 is closed )
proof end;
end;

registration
let T be non empty TopSpace;
cluster non empty open closed Element of K10( the carrier of T);
existence
ex b1 being Subset of T st
( not b1 is empty & b1 is open & b1 is closed )
proof end;
end;

theorem Th54: :: TOPS_1:54
for TS being TopSpace
for x being set
for K being Subset of TS holds
( x in Int K iff ex Q being Subset of TS st
( Q is open & Q c= K & x in Q ) )
proof end;

theorem Th55: :: TOPS_1:55
for TS being TopSpace
for GX being TopStruct
for P being Subset of TS
for R being Subset of GX holds
( ( R is open implies Int R = R ) & ( Int P = P implies P is open ) )
proof end;

theorem :: TOPS_1:56
for GX being TopStruct
for S, T being Subset of GX st S is open & S c= T holds
S c= Int T
proof end;

theorem :: TOPS_1:57
for TS being TopSpace
for P being Subset of TS holds
( P is open iff for x being set holds
( x in P iff ex Q being Subset of TS st
( Q is open & Q c= P & x in Q ) ) )
proof end;

theorem Th58: :: TOPS_1:58
for GX being TopStruct
for T being Subset of GX holds Cl (Int T) = Cl (Int (Cl (Int T)))
proof end;

theorem :: TOPS_1:59
for GX being TopStruct
for R being Subset of GX st R is open holds
Cl (Int (Cl R)) = Cl R
proof end;

definition
let GX be TopStruct ;
let R be Subset of GX;
func Fr R -> Subset of GX equals :: TOPS_1:def 2
(Cl R) /\ (Cl (R `));
coherence
(Cl R) /\ (Cl (R `)) is Subset of GX ;
end;

:: deftheorem defines Fr TOPS_1:def 2 :
for GX being TopStruct
for R being Subset of GX holds Fr R = (Cl R) /\ (Cl (R `));

theorem :: TOPS_1:60
canceled;

registration
let T be TopSpace;
let A be Subset of T;
cluster Fr A -> closed ;
coherence
Fr A is closed ;
end;

theorem Th61: :: TOPS_1:61
for GX being non empty TopSpace
for R being Subset of GX
for p being Point of GX holds
( p in Fr R iff for S being Subset of GX st S is open & p in S holds
( R meets S & R ` meets S ) )
proof end;

theorem :: TOPS_1:62
for GX being TopStruct
for T being Subset of GX holds Fr T = Fr (T `) ;

theorem :: TOPS_1:63
canceled;

theorem :: TOPS_1:64
for GX being TopStruct
for T being Subset of GX holds Fr T = ((Cl (T `)) /\ T) \/ ((Cl T) \ T)
proof end;

theorem Th65: :: TOPS_1:65
for GX being TopStruct
for T being Subset of GX holds Cl T = T \/ (Fr T)
proof end;

theorem Th66: :: TOPS_1:66
for TS being TopSpace
for K, L being Subset of TS holds Fr (K /\ L) c= (Fr K) \/ (Fr L)
proof end;

theorem Th67: :: TOPS_1:67
for TS being TopSpace
for K, L being Subset of TS holds Fr (K \/ L) c= (Fr K) \/ (Fr L)
proof end;

theorem Th68: :: TOPS_1:68
for GX being TopStruct
for T being Subset of GX holds Fr (Fr T) c= Fr T
proof end;

theorem :: TOPS_1:69
for GX being TopStruct
for R being Subset of GX st R is closed holds
Fr R c= R
proof end;

Lm1: for TS being TopSpace
for K, L being Subset of TS holds Fr K c= ((Fr (K \/ L)) \/ (Fr (K /\ L))) \/ ((Fr K) /\ (Fr L))
proof end;

theorem :: TOPS_1:70
for TS being TopSpace
for K, L being Subset of TS holds (Fr K) \/ (Fr L) = ((Fr (K \/ L)) \/ (Fr (K /\ L))) \/ ((Fr K) /\ (Fr L))
proof end;

theorem :: TOPS_1:71
for GX being TopStruct
for T being Subset of GX holds Fr (Int T) c= Fr T
proof end;

theorem :: TOPS_1:72
for GX being TopStruct
for T being Subset of GX holds Fr (Cl T) c= Fr T
proof end;

theorem Th73: :: TOPS_1:73
for GX being TopStruct
for T being Subset of GX holds Int T misses Fr T
proof end;

theorem Th74: :: TOPS_1:74
for GX being TopStruct
for T being Subset of GX holds Int T = T \ (Fr T)
proof end;

Lm2: for GX being TopStruct
for T being Subset of GX holds Fr T = (Cl T) \ (Int T)
proof end;

Lm3: for TS being TopSpace
for K being Subset of TS holds Cl (Fr K) = Fr K
proof end;

Lm4: for TS being TopSpace
for K being Subset of TS holds Int (Fr (Fr K)) = {}
proof end;

theorem :: TOPS_1:75
for TS being TopSpace
for K being Subset of TS holds Fr (Fr (Fr K)) = Fr (Fr K)
proof end;

Lm5: for X, Y, Z being set st X c= Z & Y = Z \ X holds
X c= Z \ Y
proof end;

theorem Th76: :: TOPS_1:76
for TS being TopSpace
for P being Subset of TS holds
( P is open iff Fr P = (Cl P) \ P )
proof end;

theorem Th77: :: TOPS_1:77
for TS being TopSpace
for P being Subset of TS holds
( P is closed iff Fr P = P \ (Int P) )
proof end;

definition
let GX be TopStruct ;
let R be Subset of GX;
attr R is dense means :Def3: :: TOPS_1:def 3
 Cl R = [#] GX;
end;

:: deftheorem Def3 defines dense TOPS_1:def 3 :
for GX being TopStruct
for R being Subset of GX holds
( R is dense iff Cl R = [#] GX );

registration
let GX be TopStruct ;
cluster [#] GX -> dense ;
coherence
[#] GX is dense
proof end;
end;

theorem :: TOPS_1:78
canceled;

theorem :: TOPS_1:79
for GX being TopStruct
for R, S being Subset of GX st R is dense & R c= S holds
S is dense
proof end;

theorem Th80: :: TOPS_1:80
for TS being TopSpace
for P being Subset of TS holds
( P is dense iff for Q being Subset of TS st Q <> {} & Q is open holds
P meets Q )
proof end;

theorem Th81: :: TOPS_1:81
for TS being TopSpace
for P being Subset of TS st P is dense holds
for Q being Subset of TS st Q is open holds
Cl Q = Cl (Q /\ P)
proof end;

theorem :: TOPS_1:82
for TS being TopSpace
for P, Q being Subset of TS st P is dense & Q is dense & Q is open holds
P /\ Q is dense
proof end;

definition
let GX be TopStruct ;
let R be Subset of GX;
attr R is boundary means :Def4: :: TOPS_1:def 4
R ` is dense ;
end;

:: deftheorem Def4 defines boundary TOPS_1:def 4 :
for GX being TopStruct
for R being Subset of GX holds
( R is boundary iff R ` is dense );

registration
let GX be TopStruct ;
cluster empty -> boundary Element of K10( the carrier of GX);
coherence
for b1 being Subset of GX st b1 is empty holds
b1 is boundary
proof end;
end;

theorem :: TOPS_1:83
canceled;

theorem Th84: :: TOPS_1:84
for GX being TopStruct
for R being Subset of GX holds
( R is boundary iff Int R = {} )
proof end;

registration
let GX be TopStruct ;
cluster boundary Element of K10( the carrier of GX);
existence
ex b1 being Subset of GX st b1 is boundary
proof end;
end;

registration
let GX be TopStruct ;
let R be boundary Subset of GX;
cluster Int R -> empty ;
coherence
Int R is empty by Th84;
end;

theorem Th85: :: TOPS_1:85
for TS being TopSpace
for P, Q being Subset of TS st P is boundary & Q is boundary & Q is closed holds
P \/ Q is boundary
proof end;

theorem :: TOPS_1:86
for TS being TopSpace
for P being Subset of TS holds
( P is boundary iff for Q being Subset of TS st Q c= P & Q is open holds
Q = {} )
proof end;

theorem :: TOPS_1:87
for TS being TopSpace
for P being Subset of TS st P is closed holds
( P is boundary iff for Q being Subset of TS st Q <> {} & Q is open holds
ex G being Subset of TS st
( G c= Q & G <> {} & G is open & P misses G ) )
proof end;

theorem :: TOPS_1:88
for GX being TopStruct
for R being Subset of GX holds
( R is boundary iff R c= Fr R )
proof end;

definition
let GX be TopStruct ;
let R be Subset of GX;
attr R is nowhere_dense means :Def5: :: TOPS_1:def 5
 Cl R is boundary ;
end;

:: deftheorem Def5 defines nowhere_dense TOPS_1:def 5 :
for GX being TopStruct
for R being Subset of GX holds
( R is nowhere_dense iff Cl R is boundary );

registration
let TS be TopSpace;
cluster empty -> nowhere_dense Element of K10( the carrier of TS);
coherence
for b1 being Subset of TS st b1 is empty holds
b1 is nowhere_dense
proof end;
end;

registration
let TS be TopSpace;
cluster nowhere_dense Element of K10( the carrier of TS);
existence
ex b1 being Subset of TS st b1 is nowhere_dense
proof end;
end;

theorem :: TOPS_1:89
canceled;

theorem :: TOPS_1:90
for TS being TopSpace
for P, Q being Subset of TS st P is nowhere_dense & Q is nowhere_dense holds
P \/ Q is nowhere_dense
proof end;

theorem Th91: :: TOPS_1:91
for GX being TopStruct
for R being Subset of GX st R is nowhere_dense holds
R ` is dense
proof end;

registration
let TS be TopSpace;
let R be nowhere_dense Subset of TS;
cluster R ` -> dense ;
coherence
R ` is dense by Th91;
end;

theorem Th92: :: TOPS_1:92
for GX being TopStruct
for R being Subset of GX st R is nowhere_dense holds
R is boundary
proof end;

registration
let TS be TopSpace;
cluster nowhere_dense -> boundary Element of K10( the carrier of TS);
coherence
for b1 being Subset of TS st b1 is nowhere_dense holds
b1 is boundary by Th92;
end;

theorem Th93: :: TOPS_1:93
for GX being TopStruct
for S being Subset of GX st S is boundary & S is closed holds
S is nowhere_dense
proof end;

registration
let TS be TopSpace;
cluster closed boundary -> nowhere_dense Element of K10( the carrier of TS);
coherence
for b1 being Subset of TS st b1 is boundary & b1 is closed holds
b1 is nowhere_dense by Th93;
end;

theorem :: TOPS_1:94
for GX being TopStruct
for R being Subset of GX st R is closed holds
( R is nowhere_dense iff R = Fr R )
proof end;

theorem Th95: :: TOPS_1:95
for TS being TopSpace
for P being Subset of TS st P is open holds
Fr P is nowhere_dense
proof end;

registration
let TS be TopSpace;
let P be open Subset of TS;
cluster Fr P -> nowhere_dense ;
coherence
Fr P is nowhere_dense by Th95;
end;

theorem Th96: :: TOPS_1:96
for TS being TopSpace
for P being Subset of TS st P is closed holds
Fr P is nowhere_dense
proof end;

registration
let TS be TopSpace;
let P be closed Subset of TS;
cluster Fr P -> nowhere_dense ;
coherence
Fr P is nowhere_dense by Th96;
end;

theorem Th97: :: TOPS_1:97
for TS being TopSpace
for P being Subset of TS st P is open & P is nowhere_dense holds
P = {}
proof end;

registration
let TS be TopSpace;
cluster open nowhere_dense -> empty Element of K10( the carrier of TS);
coherence
for b1 being Subset of TS st b1 is open & b1 is nowhere_dense holds
b1 is empty by Th97;
end;

definition
let GX be TopStruct ;
let R be Subset of GX;
attr R is condensed means :Def6: :: TOPS_1:def 6
( Int (Cl R) c= R & R c= Cl (Int R) );
attr R is closed_condensed means :Def7: :: TOPS_1:def 7
R = Cl (Int R);
attr R is open_condensed means :Def8: :: TOPS_1:def 8
R = Int (Cl R);
end;

:: deftheorem Def6 defines condensed TOPS_1:def 6 :
for GX being TopStruct
for R being Subset of GX holds
( R is condensed iff ( Int (Cl R) c= R & R c= Cl (Int R) ) );

:: deftheorem Def7 defines closed_condensed TOPS_1:def 7 :
for GX being TopStruct
for R being Subset of GX holds
( R is closed_condensed iff R = Cl (Int R) );

:: deftheorem Def8 defines open_condensed TOPS_1:def 8 :
for GX being TopStruct
for R being Subset of GX holds
( R is open_condensed iff R = Int (Cl R) );

theorem :: TOPS_1:98
canceled;

theorem :: TOPS_1:99
canceled;

theorem :: TOPS_1:100
canceled;

theorem Th101: :: TOPS_1:101
for GX being TopStruct
for R being Subset of GX holds
( R is open_condensed iff R ` is closed_condensed )
proof end;

theorem Th102: :: TOPS_1:102
for GX being TopStruct
for R being Subset of GX st R is closed_condensed holds
Fr (Int R) = Fr R
proof end;

theorem :: TOPS_1:103
for GX being TopStruct
for R being Subset of GX st R is closed_condensed holds
Fr R c= Cl (Int R)
proof end;

theorem Th104: :: TOPS_1:104
for GX being TopStruct
for R being Subset of GX st R is open_condensed holds
( Fr R = Fr (Cl R) & Fr (Cl R) = (Cl R) \ R )
proof end;

theorem :: TOPS_1:105
for GX being TopStruct
for R being Subset of GX st R is open & R is closed holds
( R is closed_condensed iff R is open_condensed )
proof end;

theorem Th106: :: TOPS_1:106
for TS being TopSpace
for GX being TopStruct
for P being Subset of TS
for R being Subset of GX holds
( ( R is closed & R is condensed implies R is closed_condensed ) & ( P is closed_condensed implies ( P is closed & P is condensed ) ) )
proof end;

theorem :: TOPS_1:107
for TS being TopSpace
for GX being TopStruct
for P being Subset of TS
for R being Subset of GX holds
( ( R is open & R is condensed implies R is open_condensed ) & ( P is open_condensed implies ( P is open & P is condensed ) ) )
proof end;

theorem Th108: :: TOPS_1:108
for TS being TopSpace
for P, Q being Subset of TS st P is closed_condensed & Q is closed_condensed holds
P \/ Q is closed_condensed
proof end;

theorem :: TOPS_1:109
for TS being TopSpace
for P, Q being Subset of TS st P is open_condensed & Q is open_condensed holds
P /\ Q is open_condensed
proof end;

theorem :: TOPS_1:110
for TS being TopSpace
for P being Subset of TS st P is condensed holds
Int (Fr P) = {}
proof end;

theorem :: TOPS_1:111
for GX being TopStruct
for R being Subset of GX st R is condensed holds
( Int R is condensed & Cl R is condensed )
proof end;