:: Binary Operations Applied to Functions
:: by Andrzej Trybulec
::
:: Received September 4, 1989
:: Copyright (c) 1990-2012 Association of Mizar Users

begin

theorem Th1: :: FUNCOP_1:1
for A being set holds delta A = <:(id A),(id A):>
proof end;

definition
let f be Function;
func f ~ -> Function means :Def1: :: FUNCOP_1:def 1
( dom it = dom f & ( for x being set st x in dom f holds
( ( for y, z being set st f . x = [y,z] holds
it . x = [z,y] ) & ( f . x = it . x or ex y, z being set st f . x = [y,z] ) ) ) );
existence
ex b1 being Function st
( dom b1 = dom f & ( for x being set st x in dom f holds
( ( for y, z being set st f . x = [y,z] holds
b1 . x = [z,y] ) & ( f . x = b1 . x or ex y, z being set st f . x = [y,z] ) ) ) )
proof end;
uniqueness
for b1, b2 being Function st dom b1 = dom f & ( for x being set st x in dom f holds
( ( for y, z being set st f . x = [y,z] holds
b1 . x = [z,y] ) & ( f . x = b1 . x or ex y, z being set st f . x = [y,z] ) ) ) & dom b2 = dom f & ( for x being set st x in dom f holds
( ( for y, z being set st f . x = [y,z] holds
b2 . x = [z,y] ) & ( f . x = b2 . x or ex y, z being set st f . x = [y,z] ) ) ) holds
b1 = b2
proof end;
involutiveness
for b1, b2 being Function st dom b1 = dom b2 & ( for x being set st x in dom b2 holds
( ( for y, z being set st b2 . x = [y,z] holds
b1 . x = [z,y] ) & ( b2 . x = b1 . x or ex y, z being set st b2 . x = [y,z] ) ) ) holds
( dom b2 = dom b1 & ( for x being set st x in dom b1 holds
( ( for y, z being set st b1 . x = [y,z] holds
b2 . x = [z,y] ) & ( b1 . x = b2 . x or ex y, z being set st b1 . x = [y,z] ) ) ) )
proof end;
end;

:: deftheorem Def1 defines ~ FUNCOP_1:def 1 :
for f, b2 being Function holds
( b2 = f ~ iff ( dom b2 = dom f & ( for x being set st x in dom f holds
( ( for y, z being set st f . x = [y,z] holds
b2 . x = [z,y] ) & ( f . x = b2 . x or ex y, z being set st f . x = [y,z] ) ) ) ) );

theorem Th2: :: FUNCOP_1:2
for f, g being Function holds <:f,g:> = <:g,f:> ~
proof end;

theorem Th3: :: FUNCOP_1:3
for f being Function
for A being set holds (f | A) ~ = (f ~) | A
proof end;

theorem :: FUNCOP_1:4
for A being set holds () ~ = delta A
proof end;

theorem Th5: :: FUNCOP_1:5
for f, g being Function
for A being set holds <:f,g:> | A = <:(f | A),g:>
proof end;

theorem Th6: :: FUNCOP_1:6
for f, g being Function
for A being set holds <:f,g:> | A = <:f,(g | A):>
proof end;

definition
let A, z be set ;
func A --> z -> set equals :: FUNCOP_1:def 2
[:A,{z}:];
coherence
[:A,{z}:] is set
;
end;

:: deftheorem defines --> FUNCOP_1:def 2 :
for A, z being set holds A --> z = [:A,{z}:];

registration
let A, z be set ;
coherence
( A --> z is Function-like & A --> z is Relation-like )
proof end;
end;

theorem Th7: :: FUNCOP_1:7
for A, x, z being set st x in A holds
(A --> z) . x = z
proof end;

theorem :: FUNCOP_1:8
for A, x being set st A <> {} holds
rng (A --> x) = {x} by RELAT_1:160;

theorem Th9: :: FUNCOP_1:9
for f being Function
for x being set st rng f = {x} holds
f = (dom f) --> x
proof end;

registration
let x be set ;
coherence
{} --> x is empty
by ZFMISC_1:90;
end;

registration
let x be set ;
let A be empty set ;
cluster A --> x -> empty ;
coherence
A --> x is empty
;
end;

registration
let x be set ;
let A be non empty set ;
cluster A --> x -> non empty ;
coherence
not A --> x is empty
;
end;

theorem :: FUNCOP_1:10
for x being set holds
( dom () = {} & rng () = {} ) ;

theorem Th11: :: FUNCOP_1:11
for f being Function
for x being set st ( for z being set st z in dom f holds
f . z = x ) holds
f = (dom f) --> x
proof end;

theorem Th12: :: FUNCOP_1:12
for A, x, B being set holds (A --> x) | B = (A /\ B) --> x
proof end;

theorem Th13: :: FUNCOP_1:13
for A, x being set holds
( dom (A --> x) = A & rng (A --> x) c= {x} )
proof end;

theorem Th14: :: FUNCOP_1:14
for A, x, B being set st x in B holds
(A --> x) " B = A
proof end;

theorem :: FUNCOP_1:15
for A, x being set holds (A --> x) " {x} = A
proof end;

theorem :: FUNCOP_1:16
for A, x, B being set st not x in B holds
(A --> x) " B = {}
proof end;

theorem :: FUNCOP_1:17
for h being Function
for A, x being set st x in dom h holds
h * (A --> x) = A --> (h . x)
proof end;

theorem :: FUNCOP_1:18
for h being Function
for A, x being set st A <> {} & x in dom h holds
dom (h * (A --> x)) <> {}
proof end;

theorem :: FUNCOP_1:19
for h being Function
for A, x being set holds (A --> x) * h = (h " A) --> x
proof end;

theorem :: FUNCOP_1:20
for A, x, y being set holds (A --> [x,y]) ~ = A --> [y,x]
proof end;

definition
let F, f, g be Function;
func F .: (f,g) -> set equals :: FUNCOP_1:def 3
F * <:f,g:>;
correctness
coherence
F * <:f,g:> is set
;
;
end;

:: deftheorem defines .: FUNCOP_1:def 3 :
for F, f, g being Function holds F .: (f,g) = F * <:f,g:>;

registration
let F, f, g be Function;
cluster F .: (f,g) -> Relation-like Function-like ;
coherence
( F .: (f,g) is Function-like & F .: (f,g) is Relation-like )
;
end;

Lm1: for f, g, F being Function
for x being set st x in dom (F * <:f,g:>) holds
(F * <:f,g:>) . x = F . ((f . x),(g . x))

proof end;

theorem :: FUNCOP_1:21
for f, g, F, h being Function st dom h = dom (F .: (f,g)) & ( for z being set st z in dom (F .: (f,g)) holds
h . z = F . ((f . z),(g . z)) ) holds
h = F .: (f,g)
proof end;

theorem :: FUNCOP_1:22
for f, g, F being Function
for x being set st x in dom (F .: (f,g)) holds
(F .: (f,g)) . x = F . ((f . x),(g . x)) by Lm1;

theorem Th23: :: FUNCOP_1:23
for f, g, h being Function
for A being set
for F being Function st f | A = g | A holds
(F .: (f,h)) | A = (F .: (g,h)) | A
proof end;

theorem Th24: :: FUNCOP_1:24
for f, g, h being Function
for A being set
for F being Function st f | A = g | A holds
(F .: (h,f)) | A = (F .: (h,g)) | A
proof end;

theorem Th25: :: FUNCOP_1:25
for f, g, h, F being Function holds (F .: (f,g)) * h = F .: ((f * h),(g * h))
proof end;

definition
let F, f be Function;
let x be set ;
func F [:] (f,x) -> set equals :: FUNCOP_1:def 4
F * <:f,((dom f) --> x):>;
correctness
coherence
F * <:f,((dom f) --> x):> is set
;
;
end;

:: deftheorem defines [:] FUNCOP_1:def 4 :
for F, f being Function
for x being set holds F [:] (f,x) = F * <:f,((dom f) --> x):>;

registration
let F, f be Function;
let x be set ;
cluster F [:] (f,x) -> Relation-like Function-like ;
coherence
( F [:] (f,x) is Function-like & F [:] (f,x) is Relation-like )
;
end;

theorem :: FUNCOP_1:26
for f, F being Function
for x being set holds F [:] (f,x) = F .: (f,((dom f) --> x)) ;

theorem Th27: :: FUNCOP_1:27
for f, F being Function
for x, z being set st x in dom (F [:] (f,z)) holds
(F [:] (f,z)) . x = F . ((f . x),z)
proof end;

theorem :: FUNCOP_1:28
for f, g being Function
for A being set
for F being Function
for x being set st f | A = g | A holds
(F [:] (f,x)) | A = (F [:] (g,x)) | A
proof end;

theorem Th29: :: FUNCOP_1:29
for f, h, F being Function
for x being set holds (F [:] (f,x)) * h = F [:] ((f * h),x)
proof end;

theorem :: FUNCOP_1:30
for f being Function
for A being set
for F being Function
for x being set holds (F [:] (f,x)) * (id A) = F [:] ((f | A),x)
proof end;

definition
let F be Function;
let x be set ;
let g be Function;
func F [;] (x,g) -> set equals :: FUNCOP_1:def 5
F * <:((dom g) --> x),g:>;
correctness
coherence
F * <:((dom g) --> x),g:> is set
;
;
end;

:: deftheorem defines [;] FUNCOP_1:def 5 :
for F being Function
for x being set
for g being Function holds F [;] (x,g) = F * <:((dom g) --> x),g:>;

registration
let F be Function;
let x be set ;
let g be Function;
cluster F [;] (x,g) -> Relation-like Function-like ;
coherence
( F [;] (x,g) is Function-like & F [;] (x,g) is Relation-like )
;
end;

theorem :: FUNCOP_1:31
for g, F being Function
for x being set holds F [;] (x,g) = F .: (((dom g) --> x),g) ;

theorem Th32: :: FUNCOP_1:32
for f, F being Function
for x, z being set st x in dom (F [;] (z,f)) holds
(F [;] (z,f)) . x = F . (z,(f . x))
proof end;

theorem :: FUNCOP_1:33
for f, g being Function
for A being set
for F being Function
for x being set st f | A = g | A holds
(F [;] (x,f)) | A = (F [;] (x,g)) | A
proof end;

theorem Th34: :: FUNCOP_1:34
for f, h, F being Function
for x being set holds (F [;] (x,f)) * h = F [;] (x,(f * h))
proof end;

theorem :: FUNCOP_1:35
for f being Function
for A being set
for F being Function
for x being set holds (F [;] (x,f)) * (id A) = F [;] (x,(f | A))
proof end;

theorem Th36: :: FUNCOP_1:36
for X being non empty set
for Y being set
for F being BinOp of X
for f, g being Function of Y,X holds F .: (f,g) is Function of Y,X
proof end;

definition
let X be non empty set ;
let Z be set ;
let F be BinOp of X;
let f, g be Function of Z,X;
:: original: .:
redefine func F .: (f,g) -> Function of Z,X;
coherence
F .: (f,g) is Function of Z,X
by Th36;
end;

theorem Th37: :: FUNCOP_1:37
for X, Y being non empty set
for F being BinOp of X
for f, g being Function of Y,X
for z being Element of Y holds (F .: (f,g)) . z = F . ((f . z),(g . z))
proof end;

theorem Th38: :: FUNCOP_1:38
for X, Y being non empty set
for F being BinOp of X
for f, g, h being Function of Y,X st ( for z being Element of Y holds h . z = F . ((f . z),(g . z)) ) holds
h = F .: (f,g)
proof end;

theorem :: FUNCOP_1:39
for X, Y being non empty set
for F being BinOp of X
for f being Function of Y,X
for g being Function of X,X holds (F .: ((id X),g)) * f = F .: (f,(g * f))
proof end;

theorem :: FUNCOP_1:40
for X, Y being non empty set
for F being BinOp of X
for f being Function of Y,X
for g being Function of X,X holds (F .: (g,(id X))) * f = F .: ((g * f),f)
proof end;

theorem :: FUNCOP_1:41
for X, Y being non empty set
for F being BinOp of X
for f being Function of Y,X holds (F .: ((id X),(id X))) * f = F .: (f,f)
proof end;

theorem :: FUNCOP_1:42
for X being non empty set
for F being BinOp of X
for x being Element of X
for g being Function of X,X holds (F .: ((id X),g)) . x = F . (x,(g . x))
proof end;

theorem :: FUNCOP_1:43
for X being non empty set
for F being BinOp of X
for x being Element of X
for g being Function of X,X holds (F .: (g,(id X))) . x = F . ((g . x),x)
proof end;

theorem :: FUNCOP_1:44
for X being non empty set
for F being BinOp of X
for x being Element of X holds (F .: ((id X),(id X))) . x = F . (x,x)
proof end;

theorem Th45: :: FUNCOP_1:45
for A, B, x being set st x in B holds
A --> x is Function of A,B
proof end;

definition
let I, i be set ;
:: original: -->
redefine func I --> i -> Function of I,{i};
coherence
I --> i is Function of I,{i}
proof end;
end;

definition
let B be non empty set ;
let A be set ;
let b be Element of B;
:: original: -->
redefine func A --> b -> Function of A,B;
coherence
A --> b is Function of A,B
by Th45;
end;

theorem :: FUNCOP_1:46
for A being set
for X being non empty set
for x being Element of X holds A --> x is Function of A,X ;

theorem Th47: :: FUNCOP_1:47
for X being non empty set
for Y being set
for F being BinOp of X
for f being Function of Y,X
for x being Element of X holds F [:] (f,x) is Function of Y,X
proof end;

definition
let X be non empty set ;
let Z be set ;
let F be BinOp of X;
let f be Function of Z,X;
let x be Element of X;
:: original: [:]
redefine func F [:] (f,x) -> Function of Z,X;
coherence
F [:] (f,x) is Function of Z,X
by Th47;
end;

theorem Th48: :: FUNCOP_1:48
for X, Y being non empty set
for F being BinOp of X
for f being Function of Y,X
for x being Element of X
for y being Element of Y holds (F [:] (f,x)) . y = F . ((f . y),x)
proof end;

theorem Th49: :: FUNCOP_1:49
for X, Y being non empty set
for F being BinOp of X
for g, f being Function of Y,X
for x being Element of X st ( for y being Element of Y holds g . y = F . ((f . y),x) ) holds
g = F [:] (f,x)
proof end;

theorem :: FUNCOP_1:50
for X, Y being non empty set
for F being BinOp of X
for f being Function of Y,X
for x being Element of X holds (F [:] ((id X),x)) * f = F [:] (f,x)
proof end;

theorem :: FUNCOP_1:51
for X being non empty set
for F being BinOp of X
for x being Element of X holds (F [:] ((id X),x)) . x = F . (x,x)
proof end;

theorem Th52: :: FUNCOP_1:52
for X being non empty set
for Y being set
for F being BinOp of X
for g being Function of Y,X
for x being Element of X holds F [;] (x,g) is Function of Y,X
proof end;

definition
let X be non empty set ;
let Z be set ;
let F be BinOp of X;
let x be Element of X;
let g be Function of Z,X;
:: original: [;]
redefine func F [;] (x,g) -> Function of Z,X;
coherence
F [;] (x,g) is Function of Z,X
by Th52;
end;

theorem Th53: :: FUNCOP_1:53
for X, Y being non empty set
for F being BinOp of X
for f being Function of Y,X
for x being Element of X
for y being Element of Y holds (F [;] (x,f)) . y = F . (x,(f . y))
proof end;

theorem Th54: :: FUNCOP_1:54
for X, Y being non empty set
for F being BinOp of X
for g, f being Function of Y,X
for x being Element of X st ( for y being Element of Y holds g . y = F . (x,(f . y)) ) holds
g = F [;] (x,f)
proof end;

theorem :: FUNCOP_1:55
for X being non empty set
for Y being set
for F being BinOp of X
for f being Function of Y,X
for x being Element of X holds (F [;] (x,(id X))) * f = F [;] (x,f)
proof end;

theorem :: FUNCOP_1:56
for X being non empty set
for F being BinOp of X
for x being Element of X holds (F [;] (x,(id X))) . x = F . (x,x)
proof end;

theorem :: FUNCOP_1:57
for X, Y, Z being non empty set
for f being Function of X,[:Y,Z:]
for x being Element of X holds (f ~) . x = [((f . x) 2),((f . x) 1)]
proof end;

definition
let X, Y, Z be non empty set ;
let f be Function of X,[:Y,Z:];
:: original: proj2
redefine func rng f -> Relation of Y,Z;
coherence
proj2 f is Relation of Y,Z
by RELAT_1:def 19;
end;

definition
let X, Y, Z be non empty set ;
let f be Function of X,[:Y,Z:];
:: original: ~
redefine func f ~ -> Function of X,[:Z,Y:];
coherence
f ~ is Function of X,[:Z,Y:]
proof end;
end;

theorem :: FUNCOP_1:58
for X, Y, Z being non empty set
for f being Function of X,[:Y,Z:] holds rng (f ~) = (rng f) ~
proof end;

theorem :: FUNCOP_1:59
for X being non empty set
for Y being set
for F being BinOp of X
for f being Function of Y,X
for x1, x2 being Element of X st F is associative holds
F [:] ((F [;] (x1,f)),x2) = F [;] (x1,(F [:] (f,x2)))
proof end;

theorem :: FUNCOP_1:60
for X being non empty set
for Y being set
for F being BinOp of X
for f, g being Function of Y,X
for x being Element of X st F is associative holds
F .: ((F [:] (f,x)),g) = F .: (f,(F [;] (x,g)))
proof end;

theorem :: FUNCOP_1:61
for X being non empty set
for Y being set
for F being BinOp of X
for f, g, h being Function of Y,X st F is associative holds
F .: ((F .: (f,g)),h) = F .: (f,(F .: (g,h)))
proof end;

theorem :: FUNCOP_1:62
for X being non empty set
for Y being set
for F being BinOp of X
for f being Function of Y,X
for x1, x2 being Element of X st F is associative holds
F [;] ((F . (x1,x2)),f) = F [;] (x1,(F [;] (x2,f)))
proof end;

theorem :: FUNCOP_1:63
for X being non empty set
for Y being set
for F being BinOp of X
for f being Function of Y,X
for x1, x2 being Element of X st F is associative holds
F [:] (f,(F . (x1,x2))) = F [:] ((F [:] (f,x1)),x2)
proof end;

theorem :: FUNCOP_1:64
for X being non empty set
for Y being set
for F being BinOp of X
for f being Function of Y,X
for x being Element of X st F is commutative holds
F [;] (x,f) = F [:] (f,x)
proof end;

theorem :: FUNCOP_1:65
for X being non empty set
for Y being set
for F being BinOp of X
for f, g being Function of Y,X st F is commutative holds
F .: (f,g) = F .: (g,f)
proof end;

theorem :: FUNCOP_1:66
for X being non empty set
for Y being set
for F being BinOp of X
for f being Function of Y,X st F is idempotent holds
F .: (f,f) = f
proof end;

theorem :: FUNCOP_1:67
for X, Y being non empty set
for F being BinOp of X
for f being Function of Y,X
for y being Element of Y st F is idempotent holds
(F [;] ((f . y),f)) . y = f . y
proof end;

theorem :: FUNCOP_1:68
for X, Y being non empty set
for F being BinOp of X
for f being Function of Y,X
for y being Element of Y st F is idempotent holds
(F [:] (f,(f . y))) . y = f . y
proof end;

theorem :: FUNCOP_1:69
for F, f, g being Function st [:(rng f),(rng g):] c= dom F holds
dom (F .: (f,g)) = (dom f) /\ (dom g)
proof end;

:: from PRALG_1, 2004.07.23
definition
let IT be Function;
attr IT is Function-yielding means :Def6: :: FUNCOP_1:def 6
for x being set st x in dom IT holds
IT . x is Function;
end;

:: deftheorem Def6 defines Function-yielding FUNCOP_1:def 6 :
for IT being Function holds
( IT is Function-yielding iff for x being set st x in dom IT holds
IT . x is Function );

registration
existence
ex b1 being Function st b1 is Function-yielding
proof end;
end;

registration
let B be Function-yielding Function;
let j be set ;
coherence
( B . j is Function-like & B . j is Relation-like )
proof end;
end;

registration
let F be Function-yielding Function;
let f be Function;
coherence
proof end;
end;

:: missing, 2005.11.13, A.T.
registration
let B be set ;
let c be non empty set ;
cluster B --> c -> non-empty ;
coherence
B --> c is non-empty
proof end;
end;

:: missing, 2005.12.20, A.T.
theorem :: FUNCOP_1:70
for z being set
for X, Y being non empty set
for x being Element of X
for y being Element of Y holds ([:X,Y:] --> z) . (x,y) = z
proof end;

definition
let a, b, c be set ;
func (a,b) .--> c -> Function equals :: FUNCOP_1:def 7
{[a,b]} --> c;
coherence
{[a,b]} --> c is Function
;
end;

:: deftheorem defines .--> FUNCOP_1:def 7 :
for a, b, c being set holds (a,b) .--> c = {[a,b]} --> c;

theorem :: FUNCOP_1:71
for a, b, c being set holds ((a,b) .--> c) . (a,b) = c
proof end;

:: from CQC_LANG, 2007.03.13, A.T.
definition
let x, y, a, b be set ;
func IFEQ (x,y,a,b) -> set equals :Def8: :: FUNCOP_1:def 8
a if x = y
otherwise b;
correctness
coherence
( ( x = y implies a is set ) & ( not x = y implies b is set ) )
;
consistency
for b1 being set holds verum
;
;
end;

:: deftheorem Def8 defines IFEQ FUNCOP_1:def 8 :
for x, y, a, b being set holds
( ( x = y implies IFEQ (x,y,a,b) = a ) & ( not x = y implies IFEQ (x,y,a,b) = b ) );

definition
let D be set ;
let x, y be set ;
let a, b be Element of D;
:: original: IFEQ
redefine func IFEQ (x,y,a,b) -> Element of D;
coherence
IFEQ (x,y,a,b) is Element of D
proof end;
end;

definition
let x, y be set ;
func x .--> y -> set equals :: FUNCOP_1:def 9
{x} --> y;
coherence
{x} --> y is set
;
end;

:: deftheorem defines .--> FUNCOP_1:def 9 :
for x, y being set holds x .--> y = {x} --> y;

registration
let x, y be set ;
coherence
( x .--> y is Function-like & x .--> y is Relation-like )
;
end;

registration
let x, y be set ;
coherence
x .--> y is one-to-one
proof end;
end;

theorem Th72: :: FUNCOP_1:72
for x, y being set holds (x .--> y) . x = y
proof end;

:: from SCMFSA6A, 2007.07.22, A.T.
theorem :: FUNCOP_1:73
for a, b being set
for f being Function holds
( a .--> b c= f iff ( a in dom f & f . a = b ) )
proof end;

notation
let o, m, r be set ;
synonym (o,m) :-> r for (o,m) .--> r;
end;

Lm2: for o, m, r being set holds (o,m) :-> r is Function of [:{o},{m}:],{r}
proof end;

definition
let o, m, r be set ;
:: original: .-->
redefine func (o,m) :-> r -> Function of [:{o},{m}:],{r} means :: FUNCOP_1:def 10
verum;
coherence
(o,m) .--> r is Function of [:{o},{m}:],{r}
by Lm2;
compatibility
for b1 being Function of [:{o},{m}:],{r} holds
( b1 = (o,m) .--> r iff verum )
proof end;
end;

:: deftheorem defines :-> FUNCOP_1:def 10 :
for o, m, r being set
for b4 being Function of [:{o},{m}:],{r} holds
( b4 = (o,m) :-> r iff verum );

theorem :: FUNCOP_1:74
for x, y being set holds x in dom (x .--> y)
proof end;

theorem :: FUNCOP_1:75
for z, x, y being set st z in dom (x .--> y) holds
z = x
proof end;

:: missing, 2008.04.15, A.T.
theorem :: FUNCOP_1:76
for A, x, y being set st not x in A holds
(x .--> y) | A = {}
proof end;

notation
let x, y be set ;
synonym x :-> y for x .--> y;
end;

definition
let m, o be set ;
:: original: .-->
redefine func m :-> o -> Function of {m},{o};
coherence
m .--> o is Function of {m},{o}
;
end;

theorem :: FUNCOP_1:77
for a, b, c being set
for x being Element of {a}
for y being Element of {b} holds ((a,b) :-> c) . (x,y) = c by TARSKI:def 1;

:: from MSUHOM_1, ALTCAT_1, 2008.07.06, A.T.
registration
let f be Function-yielding Function;
let C be set ;
coherence
proof end;
end;

:: from CIRCCOMB, 2008.07.06, A.T.
registration
let A be set ;
let f be Function;
coherence
proof end;
end;

:: from SEQM_3, 2008.07.17, A.T.
registration
let X, a be set ;
cluster X --> a -> constant ;
coherence
X --> a is constant
proof end;
end;

:: from YELLOW_6, 2008.07.17, A.T.
registration
existence
ex b1 being Function st
( not b1 is empty & b1 is constant )
proof end;
end;

:: missing, 2008.07.17, A.T.
registration
let f be constant Function;
let X be set ;
cluster f | X -> constant ;
coherence
f | X is constant
proof end;
end;

:: missing, 2008.08.14, A.T.
theorem :: FUNCOP_1:78
for f being constant non empty Function ex y being set st
for x being set st x in dom f holds
f . x = y
proof end;

:: from YELLOW_6, 2008.12.26, A.T.
theorem :: FUNCOP_1:79
for X being non empty set
for x being set holds the_value_of (X --> x) = x
proof end;

:: from CIRCCMB3, 2008.12.26, A.T.
theorem :: FUNCOP_1:80
for f being constant Function holds f = (dom f) --> ()
proof end;

:: missing, 2009.01.21, A.T.
registration
let X be set ;
let Y be non empty set ;
existence
ex b1 being PartFunc of X,Y st b1 is total
proof end;
end;

:: new, 2009.02.14, A.T.
registration
let I, A be set ;
cluster I --> A -> I -defined ;
coherence
I --> A is I -defined
;
end;

registration
let I, A be set ;
cluster I .--> A -> {I} -defined ;
coherence
I .--> A is {I} -defined
;
end;

:: BORSUK_1:6, 2009.06.11, A.K.
theorem :: FUNCOP_1:81
for A, B, x being set holds (A --> x) .: B c= {x} ;

registration
let I be set ;
let f be Function;
coherence ;
end;

:: 2009.10.03, A.T.
registration
let I be set ;
existence
ex b1 being non-empty I -defined Function st b1 is total
proof end;
end;

theorem Th82: :: FUNCOP_1:82
for x, y being set holds x .--> y is_isomorphism_of {[x,x]},{[y,y]}
proof end;

theorem :: FUNCOP_1:83
for x, y being set holds {[x,x]},{[y,y]} are_isomorphic
proof end;

registration
let I, A be set ;
cluster I --> A -> I -defined total for I -defined Function;
coherence
for b1 being I -defined Function st b1 = I --> A holds
b1 is total
;
end;

theorem :: FUNCOP_1:84
for x being set
for f being Function st x in dom f holds
x .--> (f . x) c= f
proof end;

registration
let A be non empty set ;
let x be set ;
let i be Element of A;
cluster x .--> i -> A -valued ;
coherence
x .--> i is A -valued
proof end;
end;

:: missing, 2010.02.10, A.T.
theorem :: FUNCOP_1:85
for X being non empty set
for F being BinOp of X
for Y being set
for f, g being Function of Y,X
for x being Element of X st F is associative holds
F .: ((F [;] (x,f)),g) = F [;] (x,(F .: (f,g)))
proof end;

registration
let A be set ;
let B be non empty set ;
let x be Element of B;
cluster A --> x -> B -valued ;
coherence
A --> x is B -valued
;
end;

registration
let A be non empty set ;
let x be Element of A;
let y be set ;
cluster x .--> y -> A -defined ;
coherence
x .--> y is A -defined
proof end;
end;

theorem :: FUNCOP_1:86
for x, y, A being set st x in A holds
(x .--> y) | A = x .--> y
proof end;

:: missing, 2011.02.06, A.K.
registration
let Y be functional set ;
coherence
for b1 being Function st b1 is Y -valued holds
b1 is Function-yielding
proof end;
end;

:: from MSUALG_4, 2011.04.16, A.T.
definition
let IT be Function;
attr IT is Relation-yielding means :: FUNCOP_1:def 11
for x being set st x in dom IT holds
IT . x is Relation;
end;

:: deftheorem defines Relation-yielding FUNCOP_1:def 11 :
for IT being Function holds
( IT is Relation-yielding iff for x being set st x in dom IT holds
IT . x is Relation );

registration
coherence
for b1 being Function st b1 is Function-yielding holds
b1 is Relation-yielding
proof end;
end;

registration
coherence
for b1 being Function st b1 is empty holds
b1 is Function-yielding
proof end;
end;

:: from CIRCCOMB, 2011.04.19, A.T.
theorem :: FUNCOP_1:87
for X, Y, x, y being set holds
( X --> x tolerates Y --> y iff ( x = y or X misses Y ) )
proof end;

theorem Th88: :: FUNCOP_1:88
for x, y being set holds rng (x .--> y) = {y}
proof end;

theorem :: FUNCOP_1:89
for z, A, x, y being set st z in A holds
(A --> x) * (y .--> z) = y .--> x
proof end;