:: Extended Euclidean Algorithm and CRT Algorithm
:: by Hiroyuki Okazaki , Yosiki Aoki and Yasunari Shidama
::
:: Received February 8, 2012
:: Copyright (c) 2012-2018 Association of Mizar Users
:: (Stowarzyszenie Uzytkownikow Mizara, Bialystok, Poland).
:: This code can be distributed under the GNU General Public Licence
:: version 3.0 or later, or the Creative Commons Attribution-ShareAlike
:: License version 3.0 or later, subject to the binding interpretation
:: detailed in file COPYING.interpretation.
:: See COPYING.GPL and COPYING.CC-BY-SA for the full text of these
:: licenses, or see http://www.gnu.org/licenses/gpl.html and
:: http://creativecommons.org/licenses/by-sa/3.0/.
environ
vocabularies RECDEF_2, TARSKI, XBOOLE_0, FINSEQ_1, RELAT_1, FUNCT_1, COMPLEX1,
NAT_1, MCART_1, ZFMISC_1, SUBSET_1, NUMBERS, INT_1, INT_2, CARD_1,
ARYTM_1, XXREAL_0, ARYTM_3, ORDINAL4, NTALGO_1, CARD_3;
notations TARSKI, XBOOLE_0, ZFMISC_1, SUBSET_1, FUNCT_1, XTUPLE_0, MCART_1,
FUNCT_2, ORDINAL1, NUMBERS, XCMPLX_0, XXREAL_0, INT_1, INT_2, NAT_1,
NAT_D, FINSEQ_1, RVSUM_1;
constructors XXREAL_0, NAT_D, REAL_1, BINARITH, RVSUM_1, XTUPLE_0;
registrations XREAL_0, RELSET_1, ORDINAL1, INT_1, SUBSET_1, FINSEQ_1, NAT_1,
XXREAL_0, XBOOLE_0, VALUED_0, CARD_1, NUMBERS, XTUPLE_0;
requirements NUMERALS, BOOLE, SUBSET, REAL, ARITHM;
definitions INT_1;
equalities FINSEQ_1, INT_1;
expansions FINSEQ_1, INT_1, FUNCT_2;
theorems TARSKI, ZFMISC_1, FUNCT_1, MCART_1, FUNCT_2, XXREAL_0, XREAL_1,
NAT_1, INT_1, INT_2, NAT_D, FINSEQ_1, FINSEQ_2, XBOOLE_1, ORDINAL1,
ABSVALUE, XCMPLX_1, INT_4, RVSUM_1, INT_6, WSIERP_1, NEWTON;
schemes FINSEQ_1, NAT_1, RECDEF_1, RECDEF_2;
begin :: Euclidean Algorithm
theorem Th1: for x,p be Integer holds (x mod p) mod p = x mod p
proof
let x,p be Integer;
x mod p = (x + 0) mod p .= ((x mod p) + (0 mod p)) mod p by NAT_D:66
.= ((x mod p) + 0) mod p by INT_4:12;
hence thesis;
end;
::==========================================================================================
::NZMATH source code
::
::def gcd(a, b):
:: """
:: Return the greatest common divisor of 2 integers a and b.
:: """
:: a, b = abs(a), abs(b)
:: while b:
:: a, b = b, a % b
:: return a
::==========================================================================================
Lm1:for a,b be Element of INT
holds
ex A,B be sequence of NAT
st
A.0 = |.a.| & B.0 = |.b.|
&
(for i be Nat holds A.(i+1) = B.i & B.(i+1) = A.i mod B.i)
proof
let a,b be Element of INT;
defpred P1[Nat,Nat,Nat,Nat,Nat ]
means
$4 = $3 & $5 = $2 mod $3;
A1: for n being Nat,
x being Element of NAT,
y being Element of NAT
ex x1 being Element of NAT,
y1 being Element of NAT st P1[n,x,y,x1,y1];
consider A be sequence of NAT,B be sequence of NAT
such that A2:
A.0 = |.a.| & B.0 = |.b.|
&
for n being Nat
holds P1[ n,A.n,B.n,A.(n + 1),B.(n + 1) ]
from RECDEF_2:sch 3(A1);
take A,B;
thus thesis by A2;
end;
Lm2:for a,b be Element of INT,
A1,B1,A2,B2 be sequence of NAT
st
( A1.0 = |.a.| & B1.0 = |.b.|
&
(for i be Nat holds A1.(i+1) = B1.i & B1.(i+1) = A1.i mod B1.i))&
(A2.0 = |.a.| & B2.0 = |.b.| &
(for i be Nat holds A2.(i+1) = B2.i & B2.(i+1) = A2.i mod B2.i))
holds
A1 = A2 & B1 = B2
proof
let a,b be Element of INT;
let A1,B1,A2,B2 be sequence of NAT;
assume A1:
A1.0 = |.a.| & B1.0 = |.b.|
&
for i be Nat holds A1.(i+1) = B1.i & B1.(i+1) = A1.i mod B1.i;
assume A2:
A2.0 = |.a.| & B2.0 = |.b.|
&
for i be Nat holds A2.(i+1) = B2.i & B2.(i+1) = A2.i mod B2.i;
defpred P[Nat] means A1.$1 = A2.$1 & B1.$1 = B2.$1;
A3: P[0] by A1,A2;
A4: for n being Nat st P[n] holds P[n+1]
proof
let n being Nat;
assume A5:P[n];
A6: A1.(n+1) = B1.n by A1
.=A2.(n+1) by A2,A5;
B1.(n+1) = A1.n mod B1.n by A1
.=B2.(n+1) by A2,A5;
hence P[n+1] by A6;
end;
for n being Nat holds P[n] from NAT_1:sch 2(A3,A4);
hence thesis;
end;
definition
let a,b be Element of INT;
func ALGO_GCD(a,b) -> Element of NAT means
:Def1:
ex A,B be sequence of NAT st
A.0 = |.a.| & B.0 = |.b.| &
(for i be Nat holds
A.(i+1) = B.i &
B.(i+1) = A.i mod B.i) &
it = A. (min*{i where i is Nat: B.i = 0} );
existence
proof
consider A,B be sequence of NAT
such that A1:
A.0 = |.a.| & B.0 = |.b.| &
(for i be Nat holds A.(i+1) = B.i & B.(i+1) = A.i mod B.i) by Lm1;
set m = A.(min*{i where i is Nat: B.i = 0});
m is Element of NAT;
hence thesis by A1;
end;
uniqueness
proof
let m1,m2 be Element of NAT;
assume ex A1,B1 be sequence of NAT
st A1.0 = |.a.| & B1.0 = |.b.|
&
(for i be Nat holds A1.(i+1) = B1.i & B1.(i+1) = A1.i mod B1.i)&
m1 = A1.(min*{i where i is Nat: B1.i = 0});
then
consider A1,B1 be sequence of NAT
such that A2:
A1.0 = |.a.| & B1.0 = |.b.|
&
(for i be Nat
holds A1.(i+1) = B1.i &
B1.(i+1) = A1.i mod B1.i) &
m1 = A1.(min*{i where i is Nat: B1.i = 0});
assume
ex A2,B2 be sequence of NAT
st
A2.0 = |.a.| & B2.0 = |.b.| &
(for i be Nat holds
A2.(i+1) = B2.i &
B2.(i+1) = A2.i mod B2.i) &
m2 = A2.(min*{i where i is Nat: B2.i = 0});
then
consider A2,B2 be sequence of NAT
such that A3:
A2.0 = |.a.| & B2.0 = |.b.|
&
(for i be Nat holds
A2.(i+1) = B2.i &
B2.(i+1) = A2.i mod B2.i) &
m2 = A2.(min*{i where i is Nat: B2.i = 0});
A1 = A2 & B1 = B2 by Lm2,A2,A3;
hence thesis by A2,A3;
end;
end;
Lm3:for a,b be Element of INT,
A,B be sequence of NAT st
(A.0 = |.a.| & B.0 = |.b.| &
(for i be Nat holds A.(i+1) = B.i & B.(i+1) = A.i mod B.i))
for i be Nat st B.i <> 0 holds A.i gcd B.i = A.(i+1) gcd B.(i+1)
proof
let a,b be Element of INT,
A,B be sequence of NAT;
assume A1:
A.0 = |.a.| & B.0 = |.b.| &
(for i be Nat holds
A.(i+1) = B.i & B.(i+1) = A.i mod B.i);
let i be Nat;
assume A2: B.i <> 0;
set k=A.i gcd B.i;
A3: A.(i+1) = B.i by A1;
A4: B.(i+1) = A.i mod B.i by A1;
A5: k divides A.(i+1) by A3,INT_2:def 2;
A6: k divides B.(i+1)
proof
A7: B.(i+1) = A.i - (A.i div B.i ) * B.i by A4,A2,INT_1:def 10;
A8: k divides A.i by INT_2:def 2;
A9: k divides B.i by INT_2:def 2;
A10:ex s being Integer
st A.i = k*s by A8;
ex t being Integer
st B.i = k*t by A9;
then
consider s,t be Integer such that
A11:B.(i+1) = (k*s) - (A.i div B.i ) * (k*t) by A7,A10;
B.(i+1) = (s - (A.i div B.i)*t ) * k by A11;
hence
k divides B.(i+1);
end;
for m being Integer
st m divides A.(i+1) & m divides B.(i+1) holds m divides k
proof
let m being Integer;
assume A12: m divides A.(i+1) & m divides B.(i+1);
then
A13: m divides B.i by A1;
A14: m divides A.i
proof
B.(i+1) = A.i - (A.i div B.i ) * B.i by A4,A2,INT_1:def 10;
then
A15: A.i = B.(i+1) + (A.i div B.i ) * B.i;
A16:ex s being Integer
st B.i = m * s by A13;
A17:ex t being Integer
st B.(i+1) = m * t by A12;
consider s,t be Integer such that
A18:A.i = (m*s) + (A.i div B.i ) * (m*t) by A15,A16,A17;
A.i = m * (s + (A.i div B.i ) * t) by A18;
hence m divides A.i;
end;
thus m divides k by A13,A14,INT_2:def 2;
end;
hence
A.(i+1) gcd B.(i+1) = k by A5,A6,INT_2:def 2;
end;
Lm4:for a,b be Element of INT,
A,B be sequence of NAT
st
(A.0 = |.a.| & B.0 = |.b.|
&
(for i be Nat holds A.(i+1) = B.i & B.(i+1) = A.i mod B.i))
holds
for i be Nat st B.i <> 0
holds
A.0 gcd B.0 = A.i gcd B.i
proof
let a,b be Element of INT,
A,B be sequence of NAT;
assume A1:
A.0 = |.a.| & B.0 = |.b.|
&
(for i be Nat holds
A.(i+1) = B.i &
B.(i+1) = A.i mod B.i);
defpred P[Nat] means
B.$1 <> 0 implies
A.0 gcd B.0 = A.$1 gcd B.$1;
A2: P[0];
A3: for i being Nat st P[i] holds P[i+1]
proof
let i being Nat;
assume A4: P[i];
B.(i+1) <> 0 implies
A.0 gcd B.0 = A.(i+1) gcd B.(i+1)
proof
assume A5: B.(i+1) <> 0;
B.i <> 0
proof
assume A6: B.i = 0;
B.(i+1) = A.i mod B.i by A1;
hence contradiction by A5,A6,INT_1:def 10;
end;
hence thesis by A4,A1,Lm3;
end;
hence P[i+1];
end;
for i being Nat holds P[i] from NAT_1:sch 2(A2,A3);
hence thesis;
end;
Lm5:for a,b be Element of INT,
A,B be sequence of NAT
st
(A.0 = |.a.| & B.0 = |.b.|
&
(for i be Nat holds A.(i+1) = B.i & B.(i+1) = A.i mod B.i))
holds
{i where i is Nat: B.i = 0} is non empty Subset of NAT
proof
let a,b be Element of INT,
A,B be sequence of NAT;
assume A1:
A.0 = |.a.| & B.0 = |.b.|
&
(for i be Nat holds A.(i+1) = B.i & B.(i+1) = A.i mod B.i);
A2:for x be object st x in {i where i is Nat: B.i = 0}
holds x in NAT
proof let x be object;
assume x in {i where i is Nat: B.i = 0};
then
ex i be Nat st x=i & B.i = 0;
hence x in NAT by ORDINAL1:def 12;
end;
ex m0 be Nat st B.m0 = 0
proof
assume A3:
not (ex m0 be Nat st B.m0 = 0);
A4: for i be Nat holds
B.(i+1) <= B.i -1
proof
let i be Nat;
A5:B.i <> 0 by A3;
B.(i+1) = A.i mod B.i by A1;
then
B.(i+1) < B.i by A5,INT_1:58;
then
B.(i+1) +1 <= B.i by NAT_1:13;
then
B.(i+1) +1 -1 <= B.i -1 by XREAL_1:9;
hence
B.(i+1) <= B.i -1;
end;
defpred P[Nat] means B.$1 <= B.0 - $1;
A6: P[0];
A7: for i be Nat st P[i] holds P[i+1]
proof
let i be Nat;
assume A8:P[i];
A9: B.(i+1) <= B.i -1 by A4;
B.i -1 <= (B.0 - i) -1 by A8,XREAL_1:9;
hence P[i+1] by A9,XXREAL_0:2;
end;
A10: for i be Nat holds P[i] from NAT_1:sch 2(A6,A7);
B.(B.0) <=B.0 - (B.0) by A10;
hence contradiction by A3,NAT_1:14;
end;
then
consider m0 be Nat such that
A11: B.m0 = 0;
m0 in {i where i is Nat: B.i = 0} by A11;
hence thesis by A2,TARSKI:def 3;
end;
theorem ::Th1:
for a,b be Element of INT
holds
ALGO_GCD(a,b) = a gcd b
proof
let a,b be Element of INT;
consider A,B be sequence of NAT such that
A1:
A.0 = |.a.| & B.0 = |.b.|
&
(for i be Nat holds A.(i+1) = B.i & B.(i+1) = A.i mod B.i)
&
ALGO_GCD(a,b)
= A. (min*{i where i is Nat: B.i = 0})
by Def1;
set m0= (min*{i where i is Nat: B.i = 0});
A2: {i where i is Nat: B.i = 0}
is non empty Subset of NAT by A1,Lm5;
then
m0 in {i where i is Nat: B.i = 0} by NAT_1:def 1;
then A3:
ex i be Nat st m0=i & B.i = 0;
per cases;
suppose A4:m0 = 0;
thus
ALGO_GCD(a,b) = A.0 gcd B.0 by A3,A4,NEWTON:52,A1
.= a gcd b by A1,INT_2:34;
end;
suppose m0 <> 0;
then
1 <= m0 by NAT_1:14;
then
1-1 <= m0-1 by XREAL_1:9;
then
reconsider m1 = m0-1 as Element of NAT by INT_1:3;
A5: B.m1 <> 0
proof
assume B.m1 = 0;
then
A6: m1 in {i where i is Nat: B.i = 0};
m0 -1 < m0 - 0 by XREAL_1:15;
hence contradiction by A6,A2,NAT_1:def 1;
end;
then
A7: A.0 gcd B.0 = A.m1 gcd B.m1 by A1,Lm4;
A8:A.m1 gcd B.m1 = A.(m1+1) gcd B.(m1+1) by Lm3,A5,A1;
A.m0 gcd B.m0
=ALGO_GCD(a,b) by A1,NEWTON:52,A3;
hence thesis by A8,A7,A1,INT_2:34;
end;
end;
begin ::Extended Euclidean Algorithm
::==========================================================================================
::NZMATH source code
::
:: def extgcd(x,y):
:: """
:: Return a tuple (u,v,d); they are the greatest common divisor d
:: of two integers x and y and u,v such that d = x * u + y * v.
:: """
:: # Crandall & Pomerance "PRIME NUMBERS",Algorithm 2.1.4
:: a,b,g,u,v,w = 1,0,x,0,1,y
:: while w:
:: q,t = divmod(g,w)
:: a,b,g,u,v,w = u,v,w,a-q*u,b-q*v,t
:: if g >= 0:
:: return (a,b,g)
:: else:
:: return (-a,-b,-g)
::==========================================================================================
scheme
QuadChoiceRec { A,B,C,D() -> non empty set,
A0() -> Element of A(),B0() -> Element of B(),
C0() -> Element of C(),D0() -> Element of D(),
P[object,object,object,object,object,object,object,object,object] }:
ex f being sequence of A(),g being sequence of B(),
h being sequence of C(),i being sequence of D()
st f.0 = A0() & g.0 = B0() &h.0 = C0() & i.0 = D0()
& for n being Nat holds P[n,f.n,g.n,h.n,i.n,f.(n+1),g.(n+1),h.(n+1),i.(n+1)]
provided
A1: for n being Nat,x being Element of A(),y being Element
of B(),z being Element of C(),w being Element of D()
ex x1 being Element of A(),y1 being Element of B(),
z1 being Element of C(),w1 being Element of D()
st P[n,x,y,z,w,x1,y1,z1,w1]
proof
defpred P1[object,object,object,object,object]
means P[$1,($2)`1,($2)`2,($3)`1,($3)`2,($4)`1,($4)`2,($5)`1,($5)`2];
A2: for n being Nat,x being Element of [:A(),B():],
y being Element of [:C(),D():]
ex z being Element of [:A(),B():],w being Element of [:C(),D():]
st P1[n,x,y,z,w]
proof
let n be Nat,x be Element of [:A(),B():],
y be Element of [:C(),D():];
x`1 is Element of A() & x`2 is Element of B()
& y`1 is Element of C() & y`2 is Element of D()
by MCART_1:10;
then
consider ai being Element of A(),bi being Element of B(),
ci being Element of C(),di being Element of D() such that
A3: P[n,x`1,x`2,y`1,y`2,ai,bi,ci,di] by A1;
reconsider z= [ai,bi]
as Element of [:A(),B():] by ZFMISC_1:87;
reconsider w= [ci,di]
as Element of [:C(),D():] by ZFMISC_1:87;
take z,w;
thus thesis by A3;
end;
reconsider
AB0=[A0(),B0()] as Element of [:A(),B():] by ZFMISC_1:87;
reconsider
CD0=[C0(),D0()] as Element of [:C(),D():] by ZFMISC_1:87;
consider fg being sequence of [:A(),B():],
hi being sequence of [:C(),D():] such that
A4: fg.0 = AB0 and
A5: hi.0 = CD0 and
A6: for e being Nat holds P1[e,fg.e,hi.e,fg.(e+1),hi.(e+1)]
from RECDEF_2:sch 3( A2);
take pr1 fg,pr2 fg,pr1 hi,pr2 hi;
(fg.0)`1 = (pr1 fg).0 & (fg.0)`2 = (pr2 fg).0
& (hi.0)`1 = (pr1 hi).0 & (hi.0)`2 = (pr2 hi).0
by FUNCT_2:def 5,def 6;
hence (pr1 fg).0 = A0() & (pr2 fg).0 = B0()
&(pr1 hi).0 = C0() & (pr2 hi).0 = D0()
by A4,A5;
let i be Nat;
A7: (fg.(i+1))`1 = (pr1 fg).(i+1) & (fg.(i+1))`2 = (pr2 fg).(i+1)
& (hi.(i+1))`1 = (pr1 hi).(i+1) & (hi.(i+1))`2 = (pr2 hi).(i+1)
by FUNCT_2:def 5,def 6;
reconsider i as Element of NAT by ORDINAL1:def 12;
(fg.i)`1 = (pr1 fg).i & (fg.i)`2 = (pr2 fg).i
& (hi.i)`1 = (pr1 hi).i & (hi.i)`2 = (pr2 hi).i
by FUNCT_2:def 5,def 6;
hence thesis by A6,A7;
end;
Lm6:for x,y be Element of INT
holds
ex g,w,q,t be sequence of INT,
a,b,v,u be sequence of INT
st
a.0 = 1 & b.0 = 0 & g.0 = x & q.0=0
& u.0 = 0 & v.0 = 1 & w.0 = y & t.0=0
&
(for i be Nat
holds
q.(i+1) = g.i div w.i & t.(i+1) = g.i mod w.i
&
a.(i+1) = u.i & b.(i+1) = v.i & g.(i+1) = w.i
&
u.(i+1) = a.i - q.(i+1)*u.i & v.(i+1) = b.i - q.(i+1)*v.i
&
w.(i+1) = t.(i+1))
proof
let x,y be Element of INT;
defpred P[Nat,Integer,Integer,Integer,Integer,
Integer,Integer,Integer,Integer]
means
$6 = $4 div $5
& $7 = $4 mod $5
& $8 = $5
& $9 = $7;
A1: for n being Nat,x being Element of INT,y being Element
of INT,z being Element of INT,w being Element of INT
ex x1 being Element of INT,y1 being Element of INT,
z1 being Element of INT,w1 being Element of INT
st P[n,x,y,z,w,x1,y1,z1,w1]
proof
let n be Nat, x,y,z,w be Element of INT;
reconsider x1 = z div w as Element of INT by INT_1:def 2;
reconsider y1 = z mod w as Element of INT by INT_1:def 2;
set z1 = w;
set w1 = y1;
take x1,y1,z1,w1;
thus P[n,x,y,z,w,x1,y1,z1,w1];
end;
reconsider i1=1 as Element of INT by INT_1:def 2;
reconsider i0=0 as Element of INT by INT_1:def 2;
consider q,t,g,w be sequence of INT such that
A2:
q.0 = i0 & t.0 =i0 & g.0 = x & w.0 = y
&
for i be Nat
holds
P[i,q.i,t.i,g.i,w.i,q.(i+1),t.(i+1),g.(i+1),w.(i+1)]
from QuadChoiceRec(A1);
defpred Q[Nat,Integer,Integer,Integer,Integer,
Integer,Integer,Integer,Integer]
means
$6 = $4
& $7 = $5
& $8 = $2 - q.($1+1)*$4
& $9 = $3 - q.($1+1)*$5;
A3: for n being Nat,
x,y,z,w being Element of INT
ex x1,y1,z1,w1 being Element of INT
st Q[n,x,y,z,w,x1,y1,z1,w1]
proof
let n being Nat,
x,y,z,w being Element of INT;
reconsider qn1=q.(n+1) as Element of INT;
set x1 = z;
set y1 = w;
reconsider z1 = x- (q.(n+1))*z as Element of INT
by INT_1:def 2;
reconsider w1 = y- (q.(n+1))*w as Element of INT
by INT_1:def 2;
take x1,y1,z1,w1;
thus Q[n,x,y,z,w,x1,y1,z1,w1];
end;
consider a,b,u,v be sequence of INT such that
A4:
a.0 = i1 & b.0 = i0 & u.0 = i0 & v.0 = i1
&
for i be Nat holds
Q[i,a.i,b.i,u.i,v.i,a.(i+1),b.(i+1),u.(i+1),v.(i+1)]
from QuadChoiceRec(A3);
take g,w,q,t,a,b,v,u;
thus thesis by A2,A4;
end;
Lm7:
for x,y be Element of INT,
g1,w1,q1,t1,
a1,b1,v1,u1,
g2,w2,q2,t2,
a2,b2,v2,u2 be sequence of INT
st
( a1.0 = 1 & b1.0 = 0 & g1.0 = x & q1.0=0
& u1.0 = 0 & v1.0 = 1 & w1.0 = y & t1.0=0
&
(for i be Nat
holds
q1.(i+1) = g1.i div w1.i & t1.(i+1) = g1.i mod w1.i
&
a1.(i+1) = u1.i & b1.(i+1) = v1.i & g1.(i+1) = w1.i
&
u1.(i+1) = a1.i - q1.(i+1)*u1.i & v1.(i+1)
= b1.i - q1.(i+1)*v1.i
&
w1.(i+1) = t1.(i+1)) )
&
( a2.0 = 1 & b2.0 = 0 & g2.0 = x & q2.0=0
& u2.0 = 0 & v2.0 = 1 & w2.0 = y & t2.0=0
&
(for i be Nat
holds
q2.(i+1) = g2.i div w2.i & t2.(i+1) = g2.i mod w2.i
&
a2.(i+1) = u2.i & b2.(i+1) = v2.i & g2.(i+1) = w2.i
&
u2.(i+1) = a2.i - q2.(i+1)*u2.i & v2.(i+1)
= b2.i - q2.(i+1)*v2.i
&
w2.(i+1) = t2.(i+1)) )
holds
g1=g2 & w1 = w2 & q1 = q2 & t1 = t2
& a1=a2 & b1 = b2 & v1 =v2 & u1 = u2
proof
let x,y be Element of INT,
g1,w1,q1,t1,
a1,b1,v1,u1,
g2,w2,q2,t2,
a2,b2,v2,u2 be sequence of INT;
assume A1:
( a1.0 = 1 & b1.0 = 0 & g1.0 = x & q1.0=0
& u1.0 = 0 & v1.0 = 1 & w1.0 = y & t1.0=0
&
(for i be Nat
holds
q1.(i+1) = g1.i div w1.i & t1.(i+1) = g1.i mod w1.i
&
a1.(i+1) = u1.i & b1.(i+1) = v1.i & g1.(i+1) = w1.i
&
u1.(i+1) = a1.i - q1.(i+1)*u1.i & v1.(i+1) = b1.i - q1.(i+1)*v1.i
&
w1.(i+1) = t1.(i+1)) );
assume A2:
( a2.0 = 1 & b2.0 = 0 & g2.0 = x & q2.0=0
& u2.0 = 0 & v2.0 = 1 & w2.0 = y & t2.0=0
&
(for i be Nat
holds
q2.(i+1) = g2.i div w2.i & t2.(i+1) = g2.i mod w2.i
&
a2.(i+1) = u2.i & b2.(i+1) = v2.i & g2.(i+1) = w2.i
&
u2.(i+1) = a2.i - q2.(i+1)*u2.i & v2.(i+1) = b2.i - q2.(i+1)*v2.i
&
w2.(i+1) = t2.(i+1)) );
defpred P[Nat] means
g1.$1 =g2.$1 & w1.$1 =w2.$1 & q1.$1 =q2.$1 & t1.$1 = t2.$1 &
a1.$1 =a2.$1 & b1.$1 =b2.$1 & v1.$1 =v2.$1 & u1.$1 = u2.$1;
A3: P[0] by A1,A2;
A4: for n being Nat st P[n] holds P[n+1]
proof
let n being Nat;
assume A5:P[n];
A6: q1.(n+1)
=g2.n div w2.n by A1,A5
.= q2.(n+1) by A2;
A7:t1.(n+1)
= g2.n mod w2.n by A1,A5
.= t2.(n+1) by A2;
A8:a1.(n+1)
= u2.n by A1,A5
.= a2.(n+1) by A2;
A9: b1.(n+1)
= v2.n by A5,A1
.= b2.(n+1) by A2;
A10: g1.(n+1)
= w2.n by A5,A1
.= g2.(n+1) by A2;
A11: u1.(n+1)
= a2.n - q1.(n+1)*u2.n by A1,A5
.= u2.(n+1) by A2,A6;
A12: v1.(n+1)
= b2.n - q1.(n+1)*v2.n by A5,A1
.= v2.(n+1) by A2,A6;
w1.(n+1)
=t2.(n+1) by A7,A1
.= w2.(n+1) by A2;
hence P[n+1] by A6,A7,A8,A9,A10,A11,A12;
end;
for n being Nat holds P[n] from NAT_1:sch 2(A3,A4);
hence thesis;
end;
definition
let x,y be Element of INT;
func ALGO_EXGCD(x,y) -> Element of [:INT,INT,INT:] means
:Def2:
ex g,w,q,t be sequence of INT,
a,b,v,u be sequence of INT,
istop be Nat
st
a.0 = 1 & b.0 = 0 & g.0 = x & q.0 =0
& u.0 = 0 & v.0 = 1 & w.0 = y & t.0 =0
&
(for i be Nat
holds
q.(i+1) = g.i div w.i & t.(i+1) = g.i mod w.i
&
a.(i+1) = u.i & b.(i+1) = v.i & g.(i+1) = w.i
&
u.(i+1) = a.i - q.(i+1)*u.i & v.(i+1) = b.i - q.(i+1)*v.i
&
w.(i+1) = t.(i+1))
& istop = min*{i where i is Nat: w.i = 0}
& (0 <= g.istop implies it =[a.istop,b.istop,g.istop] )
& (g.istop < 0 implies it =[-(a.istop),-(b.istop),-(g.istop)] );
existence
proof
consider g,w,q,t be sequence of INT,
a,b,v,u be sequence of INT such that
A1:
a.0 = 1 & b.0 = 0 & g.0 = x & q.0=0
& u.0 = 0 & v.0 = 1 & w.0 = y & t.0=0
&
(for i be Nat
holds
q.(i+1) = g.i div w.i & t.(i+1) = g.i mod w.i
&
a.(i+1) = u.i & b.(i+1) = v.i & g.(i+1) = w.i
&
u.(i+1) = a.i - q.(i+1)*u.i & v.(i+1) = b.i - q.(i+1)*v.i
&
w.(i+1) = t.(i+1)) by Lm6;
set istop = min*{i where i is Nat: w.i = 0};
now per cases;
suppose A2:0 <= g.istop;
[a.istop,b.istop,g.istop] in [:INT,INT,INT:]
by MCART_1:69;
hence
ex xx be Element of [:INT,INT,INT:]
st
(0 <= g.istop implies xx =[a.istop,b.istop,g.istop] )
& (g.istop < 0 implies xx =[-(a.istop),-(b.istop),-(g.istop)] )
by A2;
end;
suppose A3:g.istop < 0;
A4: - g.istop in INT by INT_1:def 2;
-a.istop in INT & -b.istop in INT by INT_1:def 2;
then
[-a.istop,-b.istop,-g.istop] in [:INT,INT,INT:]
by A4,MCART_1:69;
hence
ex xx be Element of [:INT,INT,INT:]
st
(0 <= g.istop implies xx =[a.istop,b.istop,g.istop] )
& (g.istop < 0 implies xx =[-(a.istop),-(b.istop),-(g.istop)] )
by A3;
end;
end;
then
consider xx be Element of [:INT,INT,INT:] such that
A5:
(0 <= g.istop implies xx =[a.istop,b.istop,g.istop] )
& (g.istop < 0 implies xx =[-(a.istop),-(b.istop),-(g.istop)] );
take xx;
thus thesis by A1,A5;
end;
uniqueness
proof
let s1,s2 be Element of [:INT,INT,INT:];
assume A6:
ex g1,w1,q1,t1,a1,b1,v1,u1 be sequence of INT,
istop1 be Nat
st
( a1.0 = 1 & b1.0 = 0 & g1.0 = x & q1.0=0
& u1.0 = 0 & v1.0 = 1 & w1.0 = y & t1.0=0
&
(for i be Nat
holds
q1.(i+1) = g1.i div w1.i & t1.(i+1) = g1.i mod w1.i
&
a1.(i+1) = u1.i & b1.(i+1) = v1.i & g1.(i+1) = w1.i
&
u1.(i+1) = a1.i - q1.(i+1)*u1.i & v1.(i+1) = b1.i - q1.(i+1)*v1.i
&
w1.(i+1) = t1.(i+1)) )
& istop1 = min*{i where i is Nat: w1.i = 0}
& (0 <= g1.istop1 implies s1 =[a1.istop1,b1.istop1,g1.istop1] )
& (g1.istop1 < 0 implies s1 =[-(a1.istop1),-(b1.istop1),-(g1.istop1)] );
assume
A7:
ex g2,w2,q2,t2 be sequence of INT,
a2,b2,v2,u2 be sequence of INT,
istop2 be Nat
st
( a2.0 = 1 & b2.0 = 0 & g2.0 = x & q2.0=0
& u2.0 = 0 & v2.0 = 1 & w2.0 = y & t2.0=0
&
(for i be Nat
holds
q2.(i+1) = g2.i div w2.i & t2.(i+1) = g2.i mod w2.i
&
a2.(i+1) = u2.i & b2.(i+1) = v2.i & g2.(i+1) = w2.i
&
u2.(i+1) = a2.i - q2.(i+1)*u2.i & v2.(i+1) = b2.i - q2.(i+1)*v2.i
&
w2.(i+1) = t2.(i+1)) )
& istop2 = min*{i where i is Nat: w2.i = 0}
& (0 <= g2.istop2 implies s2 =[a2.istop2,b2.istop2,g2.istop2] )
& (g2.istop2 < 0 implies s2 =[-(a2.istop2),-(b2.istop2),-(g2.istop2)] );
consider
g1,w1,q1,t1 be sequence of INT,
a1,b1,v1,u1 be sequence of INT,
istop1 be Nat
such that A8:
( a1.0 = 1 & b1.0 = 0 & g1.0 = x & q1.0=0
& u1.0 = 0 & v1.0 = 1 & w1.0 = y & t1.0=0
&
(for i be Nat
holds
q1.(i+1) = g1.i div w1.i & t1.(i+1) = g1.i mod w1.i
&
a1.(i+1) = u1.i & b1.(i+1) = v1.i & g1.(i+1) = w1.i
&
u1.(i+1) = a1.i - q1.(i+1)*u1.i & v1.(i+1)
= b1.i - q1.(i+1)*v1.i
&
w1.(i+1) = t1.(i+1)) )
& istop1 = min*{k where k is Nat: w1.k = 0}
& (0 <= g1.istop1 implies s1 =[a1.istop1,b1.istop1,g1.istop1] )
& (g1.istop1 < 0 implies s1 =[-(a1.istop1),-(b1.istop1),-(g1.istop1)] )
by A6;
consider
g2,w2,q2,t2 be sequence of INT,
a2,b2,v2,u2 be sequence of INT,
istop2 be Nat
such that A9:
( a2.0 = 1 & b2.0 = 0 & g2.0 = x & q2.0=0
& u2.0 = 0 & v2.0 = 1 & w2.0 = y & t2.0=0
&
(for i be Nat
holds
q2.(i+1) = g2.i div w2.i & t2.(i+1) = g2.i mod w2.i
&
a2.(i+1) = u2.i & b2.(i+1) = v2.i & g2.(i+1) = w2.i
& u2.(i+1) = a2.i - q2.(i+1)*u2.i
& v2.(i+1) = b2.i - q2.(i+1)*v2.i
&
w2.(i+1) = t2.(i+1)) )
& istop2 = min*{k where k is Nat: w2.k = 0}
& (0 <= g2.istop2 implies s2 =[a2.istop2,b2.istop2,g2.istop2] )
& (g2.istop2 < 0 implies s2 =[-(a2.istop2),-(b2.istop2),-(g2.istop2)] )
by A7;
g1=g2 & w1=w2 & a1=a2 & b1=b2 by A8,A9,Lm7;
hence s1=s2 by A8,A9;
end;
end;
Lm8:for a,b be Element of INT,
A,B be sequence of INT
st
(A.0 = a & B.0 = b
&
(for i be Nat holds A.(i+1) = B.i & B.(i+1) = A.i mod B.i))
holds
for i be Nat st B.i <> 0
holds
A.i gcd B.i = A.(i+1) gcd B.(i+1)
proof
let a,b be Element of INT,
A,B be sequence of INT;
assume A1:
A.0 = a & B.0 = b
&
(for i be Nat
holds
A.(i+1) = B.i
&
B.(i+1) = A.i mod B.i);
let i be Nat;
assume A2: B.i <> 0;
set k=A.i gcd B.i;
A3: A.(i+1) = B.i by A1;
A4: B.(i+1) = A.i mod B.i by A1;
A5: k divides A.(i+1) by A3,INT_2:def 2;
A6: k divides B.(i+1)
proof
A7: B.(i+1) = A.i - (A.i div B.i ) * B.i by A4,A2,INT_1:def 10;
A8: k divides A.i by INT_2:def 2;
A9: k divides B.i by INT_2:def 2;
A10:ex s being Integer
st A.i = k*s by A8;
ex t being Integer
st B.i = k*t by A9;
then
consider s,t be Integer such that
A11:B.(i+1) = (k*s) - (A.i div B.i ) * (k*t) by A7,A10;
B.(i+1) = (s - (A.i div B.i)*t ) * k by A11;
hence
k divides B.(i+1);
end;
for m being Integer
st m divides A.(i+1) & m divides B.(i+1) holds m divides k
proof
let m be Integer;
assume A12: m divides A.(i+1) & m divides B.(i+1);
then
A13: m divides B.i by A1;
A14: m divides A.i
proof
B.(i+1) = A.i - (A.i div B.i ) * B.i by A4,A2,INT_1:def 10;
then
A15: A.i = B.(i+1) + (A.i div B.i ) * B.i;
A16:ex s being Integer
st B.i = m * s by A13;
A17:ex t being Integer
st B.(i+1) = m * t by A12;
consider s,t be Integer such that
A18:A.i = (m*s) + (A.i div B.i ) * (m*t) by A15,A16,A17;
A.i = m * (s + (A.i div B.i ) * t) by A18;
hence m divides A.i;
end;
thus m divides k by A13,A14,INT_2:def 2;
end;
hence
A.(i+1) gcd B.(i+1) = k by A5,A6,INT_2:def 2;
end;
Lm9:for a,b be Element of INT,
A,B be sequence of INT
st
(A.0 = a & B.0 = b
&
(for i be Nat
holds
A.(i+1) = B.i
&
B.(i+1) = A.i mod B.i))
holds
for i be Nat st B.i <> 0
holds
A.0 gcd B.0 = A.i gcd B.i
proof
let a,b be Element of INT,
A,B be sequence of INT;
assume A1:
A.0 = a & B.0 = b
&
(for i be Nat
holds
A.(i+1) = B.i
&
B.(i+1) = A.i mod B.i);
defpred P[Nat] means
B.$1 <> 0 implies A.0 gcd B.0 = A.$1 gcd B.$1;
A2: P[0];
A3: for i being Nat st P[i] holds P[i+1]
proof
let i being Nat;
assume A4: P[i];
B.(i+1) <> 0 implies
A.0 gcd B.0 = A.(i+1) gcd B.(i+1)
proof
assume A5: B.(i+1) <> 0;
B.i <> 0
proof
assume A6: B.i = 0;
B.(i+1) = A.i mod B.i by A1;
hence contradiction by A5,A6,INT_1:def 10;
end;
hence thesis by A4,A1,Lm8;
end;
hence P[i+1];
end;
for i being Nat holds P[i] from NAT_1:sch 2(A2,A3);
hence thesis;
end;
theorem Th3:
for i2,i1 being Integer st i2 <= 0 holds i1 mod i2 <= 0
proof
let i2,i1 be Integer;
assume A1: i2 <= 0;
per cases by A1;
suppose A2: i2 < 0;
[\(i1 / i2)/] <= i1 / i2 by INT_1:def 6;
then (i1 / i2) * i2 <= (i1 div i2) * i2
by A2,XREAL_1:65;
then i1 <= (i1 div i2) * i2 by A2,XCMPLX_1:87;
then i1 - ((i1 div i2) * i2) <= 0 by XREAL_1:47;
hence i1 mod i2 <= 0 by INT_1:def 10;
end;
suppose i2 = 0;
hence i1 mod i2 <= 0 by INT_1:def 10;
end;
end;
theorem Th4:
for i2,i1 being Integer st i2 < 0 holds -(i1 mod i2) < -i2
proof
let i2,i1 be Integer;
assume A1: i2 <0;
(i1 / i2) - 1 < [\(i1 / i2)/] by INT_1:def 6;
then (i1 div i2) * i2 < ((i1 / i2) - 1) * i2 by A1,XREAL_1:69;
then (i1 div i2) * i2 < ((i1 / i2) * i2) - (1 * i2);
then ((i1 div i2) * i2) < i1 - i2 by A1,XCMPLX_1:87;
then ((i1 div i2) * i2) -i1 < i1 -i2 - i1 by XREAL_1:14;
then -(i1- ((i1 div i2) * i2) ) < -i2;
hence -( i1 mod i2) < -i2 by A1,INT_1:def 10;
end;
theorem Th5:
for x,y be Element of INT st |.y.| <> 0 holds
|.x mod y.| < |.y.|
proof
let x,y be Element of INT;
assume A1: |.y.| <> 0;
per cases;
suppose A2: 0 < y;
then
A3: x mod y < y by INT_1:58;
0 <= x mod y by A2,INT_1:57;
then
A4: |.x mod y.| < y by A3,ABSVALUE:def 1;
y <= |.y.| by ABSVALUE:4;
hence |.x mod y.| < |.y.| by A4,XXREAL_0:2;
end;
suppose A5: y <= 0;
A6:y <> 0 by A1,ABSVALUE:2;
A7: -(x mod y) < -y by Th4,A6,A5;
A8: (x mod y) <=0 by A5,Th3;
A9: |.x mod y.| = -(x mod y)
proof
per cases;
suppose x mod y = 0;
hence
|.x mod y.| = -(x mod y) by ABSVALUE:2;
end;
suppose x mod y <> 0;
hence
|.x mod y.| = -(x mod y) by A8,ABSVALUE:def 1;
end;
end;
thus |.x mod y.| < |.y.| by A9,A7,A6,A5,ABSVALUE:def 1;
end;
end;
Lm10:for a,b be Element of INT,
A,B be sequence of INT
st
(A.0 = a & B.0 = b
&
(for i be Nat
holds
A.(i+1) = B.i
&
B.(i+1) = A.i mod B.i))
holds
{i where i is Nat: B.i = 0}
is non empty Subset of NAT
proof
let a,b be Element of INT,
A,B be sequence of INT;
assume A1:
A.0 = a & B.0 = b
&
(for i be Nat
holds
A.(i+1) = B.i
&
B.(i+1) = A.i mod B.i);
A2: for x be object
st x in
{i where i is Nat: B.i = 0}
holds x in NAT
proof let x be object;
assume x in {i where i is Nat: B.i = 0};
then
ex i be Nat st x=i & B.i = 0;
hence x in NAT by ORDINAL1:def 12;
end;
ex m0 be Nat st B.m0 = 0
proof
assume A3:not (ex m0 be Nat st B.m0 = 0);
A4: for m0 be Nat holds |.B.m0.| <> 0
by A3,ABSVALUE:2;
A5: for i be Nat holds |.B.(i+1).| <= |.B.i.| -1
proof
let i be Nat;
|.B.(i+1).| = |.A.i mod B.i.| by A1;
then
|.B.(i+1).| < |.B.i.| by A4,Th5;
then
|.B.(i+1).| +1 <= |.B.i.| by NAT_1:13;
then
|.B.(i+1).| +1 -1 <= |.B.i.| -1 by XREAL_1:9;
hence
|.B.(i+1).| <= |.B.i.| -1;
end;
defpred P[Nat] means |.B.$1.| <= |.B.0 .| - $1;
A6: P[0];
A7:
for i be Nat st P[i] holds P[i+1]
proof
let i be Nat;
assume A8:P[i];
A9: |.B.(i+1).| <= |.B.i.| -1 by A5;
|.B.i.| -1 <= (|.B.0 .| - i) -1 by A8,XREAL_1:9;
hence P[i+1] by A9,XXREAL_0:2;
end;
A10: for i be Nat holds P[i] from NAT_1:sch 2(A6,A7);
|. B. |.B.0 .| .| <=|.B.0 .| - |.(B.0).| by A10;
hence contradiction by A4,NAT_1:14;
end;
then
consider m0 be Nat such that
A11: B.m0 = 0;
m0 in {i where i is Nat: B.i = 0} by A11;
hence thesis by A2,TARSKI:def 3;
end;
Lm11: for a be Element of INT holds a gcd 0 = |.a.| by WSIERP_1:8;
Lm12:
for x,y be Element of INT,
g,w,q,t be sequence of INT,
a,b,v,u be sequence of INT
st
a.0 = 1 & b.0 = 0 & g.0 = x & q.0 =0
& u.0 = 0 & v.0 = 1 & w.0 = y & t.0 =0
&
(for i be Nat
holds
q.(i+1) = g.i div w.i & t.(i+1) = g.i mod w.i
&
a.(i+1) = u.i & b.(i+1) = v.i & g.(i+1) = w.i
&
u.(i+1) = a.i - q.(i+1)*u.i & v.(i+1) = b.i - q.(i+1)*v.i
&
w.(i+1) = t.(i+1))
holds
for i be Nat
st w.i <> 0
holds
a.(i+1) * x + b.(i+1) * y = g.(i+1)
proof
let x,y be Element of INT,
g,w,q,t be sequence of INT,
a,b,v,u be sequence of INT;
assume A1:
a.0 = 1 & b.0 = 0 & g.0 = x & q.0 =0
& u.0 = 0 & v.0 = 1 & w.0 = y & t.0 =0
&
for i be Nat
holds
q.(i+1) = g.i div w.i & t.(i+1) = g.i mod w.i
&
a.(i+1) = u.i & b.(i+1) = v.i & g.(i+1) = w.i
&
u.(i+1) = a.i - q.(i+1)*u.i & v.(i+1) = b.i - q.(i+1)*v.i
&
w.(i+1) = t.(i+1);
defpred P[Nat] means
w.$1 <> 0
implies
(a.($1) * x + b.($1) * y = g.($1)
&
a.($1+1) * x + b.($1+1) * y = g.($1+1));
A2:P[0]
proof
assume w.0 <> 0;
reconsider I0=0 as Element of NAT;
a.(I0 + 1) *x + b.(I0 + 1)* y
= (u.0)*x + b.(I0 + 1) *y by A1
.= 0 *x + 1 *y by A1
.= g.(I0 + 1) by A1;
hence thesis by A1;
end;
A3: for i be Nat st P[i] holds P[i+1]
proof
let i be Nat;
assume A4: P[i];
assume A5: w.(i+1) <> 0;
A6: w.i <> 0
proof
assume
A7:w.i = 0;
t.(i+1) = g.i mod w.i by A1
.= 0 by A7,INT_1:def 10;
hence contradiction by A1,A5;
end;
a.((i+1)+1) *x + b.((i+1)+1)* y
= (u.(i+1))*x + b.((i+1)+1) *y by A1
.= (u.(i+1))*x + (v.(i+1)) *y by A1
.= (a.i - q.(i+1)*u.i)*x + (v.(i+1)) *y by A1
.= (a.i - q.(i+1)*u.i)*x + (b.i - q.(i+1)*v.i) *y by A1
.= g.i -q.(i+1)*(u.i*x + v.i*y ) by A6,A4
.= g.i -q.(i+1)* (a.(i+1)*x + v.i*y) by A1
.= g.i -q.(i+1)* g.(i+1) by A6,A4,A1
.= g.i -(g.i div w.i)*g.(i+1) by A1
.= g.i -(g.i div w.i)*w.i by A1
.= g.i mod w.i by A6,INT_1:def 10
.= t.(i+1) by A1
.= w.(i+1) by A1
.= g.((i+1)+1) by A1;
hence thesis by A6,A4;
end;
for i be Nat holds P[i] from NAT_1:sch 2(A2,A3);
hence thesis;
end;
theorem Th6:
for x,y be Element of INT
holds
ALGO_EXGCD(x,y)`3_3 = x gcd y
&
ALGO_EXGCD(x,y)`1_3 * x + ALGO_EXGCD(x,y)`2_3 * y
= x gcd y
proof
let x,y be Element of INT;
consider g,w,q,t be sequence of INT,
a,b,v,u be sequence of INT,
istop be Nat such that
A1:
a.0 = 1 & b.0 = 0 & g.0 = x & q.0 =0
& u.0 = 0 & v.0 = 1 & w.0 = y & t.0 =0
&
(for i be Nat
holds
q.(i+1) = g.i div w.i & t.(i+1) = g.i mod w.i
&
a.(i+1) = u.i & b.(i+1) = v.i & g.(i+1) = w.i
&
u.(i+1) = a.i - q.(i+1)*u.i & v.(i+1) = b.i - q.(i+1)*v.i
&
w.(i+1) = t.(i+1))
& istop = min*{i where i is Nat: w.i = 0}
& (0 <= g.istop implies ALGO_EXGCD(x,y)
=[a.istop,b.istop,g.istop] )
& (g.istop < 0 implies ALGO_EXGCD(x,y)
=[-(a.istop),-(b.istop),-(g.istop)] )
by Def2;
A2:
now let i be Nat;
thus g.(i+1) = w.i by A1;
thus w.(i+1) = t.(i+1) by A1
.= g.i mod w.i by A1;
end;
A3: {i where i is Nat: w.i = 0}
is non empty Subset of NAT by A1,A2,Lm10;
then
istop in {i where i is Nat: w.i = 0} by A1,NAT_1:def 1;
then
A4: ex i be Nat st istop=i & w.i = 0;
A5: ALGO_EXGCD(x,y)`3_3 = |.g.istop.|
proof
per cases;
suppose 0 <= g.istop;
then
|.g.istop.| = g.istop by ABSVALUE:def 1;
hence
ALGO_EXGCD(x,y)`3_3 = |.g.istop.| by A1;
end;
suppose A6: g.istop < 0;
then
|.g.istop.| = -g.istop by ABSVALUE:def 1;
hence
ALGO_EXGCD(x,y)`3_3 = |.g.istop.| by A1,A6;
end;
end;
per cases;
suppose A7:istop = 0;
thus
A8: ALGO_EXGCD(x,y)`3_3
= x gcd y by A1,A4,Lm11,A5,A7;
thus
ALGO_EXGCD(x,y)`1_3 * x + ALGO_EXGCD(x,y)`2_3 * y
= x gcd y
proof
per cases;
suppose 0 <= g.istop;
thus
ALGO_EXGCD(x,y)`1_3 * x + ALGO_EXGCD(x,y)`2_3 * y
= x gcd y by A1,A7,A8;
end;
suppose g.istop < 0;
thus
ALGO_EXGCD(x,y)`1_3 * x + ALGO_EXGCD(x,y)`2_3 * y
= x gcd y by A1,A7,A8;
end;
end;
end;
suppose istop <> 0;
then
1 <= istop by NAT_1:14;
then
1-1 <= istop-1 by XREAL_1:9;
then
reconsider
m1 = istop-1 as Element of NAT by INT_1:3;
A9: w.m1 <> 0
proof
assume w.m1 = 0;
then
A10:m1 in {i where i is Nat: w.i = 0};
istop -1 < istop - 0 by XREAL_1:15;
hence contradiction by A10,A1,A3,NAT_1:def 1;
end;
A11: g.m1 gcd w.m1 = g.(m1+1) gcd w.(m1+1) by Lm8,A1,A9,A2;
A12: g.(istop) gcd w.(istop)
= ALGO_EXGCD(x,y)`3_3 by A5,Lm11,A4;
hence
A13:ALGO_EXGCD(x,y)`3_3 = x gcd y by A11,A9,A2,Lm9,A1;
A14:a.(m1+1) * x + b.(m1+1) * y = g.(m1+1)
by A9,Lm12,A1;
thus
ALGO_EXGCD(x,y)`1_3 * x + ALGO_EXGCD(x,y)`2_3 * y
= x gcd y
proof
per cases;
suppose 0 <= g.istop;
thus
ALGO_EXGCD(x,y)`1_3 * x + ALGO_EXGCD(x,y)`2_3 * y
= x gcd y by A13,A14,A1;
end;
suppose g.istop < 0;
thus
ALGO_EXGCD(x,y)`1_3 * x + ALGO_EXGCD(x,y)`2_3 * y
= x gcd y by A14,A12,A11,A9,A2,Lm9,A1;
end;
end;
end;
end;
::==========================================================================================
::NZMATH source code
:: def inverse(x,p):
:: """
:: This function returns inverse of x for modulo p.
:: """
:: x = x % p
:: y = gcd.extgcd(p,x)
:: if y[2] == 1:
:: if y[1] < 0:
:: r = p + y[1]
:: return r
:: else:
:: return y[1]
:: raise ZeroDivisionError("There is no inverse for %d modulo %d." % (x,p))
::=======================================================================================
definition
let x,p be Element of INT;
func ALGO_INVERSE(x,p) -> Element of INT means
:Def3:
for y be Element of INT st y = (x mod p) holds
( ALGO_EXGCD(p,y)`3_3 = 1 implies
( ( ALGO_EXGCD(p,y)`2_3 < 0) implies
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& it = p + z ))
&
( (0 <= ALGO_EXGCD(p,y)`2_3) implies it = ALGO_EXGCD(p,y)`2_3)
)
&
( ALGO_EXGCD(p,y)`3_3 <> 1 implies it = {} );
existence
proof
reconsider y = x mod p as Element of INT by INT_1:def 2;
now per cases;
suppose A1: ALGO_EXGCD(p,y)`3_3 = 1;
now per cases;
suppose A2: ( ALGO_EXGCD(p,y)`2_3 < 0);
reconsider z = ALGO_EXGCD(p,y)`2_3
as Element of INT;
reconsider s = p + z
as Element of INT by INT_1:def 2;
ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& s = p + z;
hence ex s be Element of INT st
( ( ALGO_EXGCD(p,y)`2_3 < 0) implies
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& s = p + z ) )
&
( (0 <= ALGO_EXGCD(p,y)`2_3) implies s = ALGO_EXGCD(p,y)`2_3 )
&
( ALGO_EXGCD(p,y)`3_3 <> 1 implies s = {} )
by A2,A1;
end;
suppose A3: ( 0 <= ALGO_EXGCD(p,y)`2_3 );
reconsider s = ALGO_EXGCD(p,y)`2_3
as Element of INT;
thus ex s be Element of INT st
( ( ALGO_EXGCD(p,y)`2_3 < 0) implies
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& s = p + z ) )
&
( (0 <= ALGO_EXGCD(p,y)`2_3) implies s = ALGO_EXGCD(p,y)`2_3 )
&
( ALGO_EXGCD(p,y)`3_3 <> 1 implies s = {} )
by A3,A1;
end;
end;
hence
ex s be Element of INT st
( ALGO_EXGCD(p,y)`3_3 = 1 implies
( ( ALGO_EXGCD(p,y)`2_3 < 0) implies
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& s = p + z ))
&
( (0 <= ALGO_EXGCD(p,y)`2_3) implies s = ALGO_EXGCD(p,y)`2_3)
)
&
( ALGO_EXGCD(p,y)`3_3 <> 1 implies s = {} );
end;
suppose A4: ALGO_EXGCD(p,y)`3_3 <> 1;
reconsider s ={} as Element of INT by INT_1:def 2;
ALGO_EXGCD(p,y)`3_3 <> 1 implies s = {};
hence
ex s be Element of INT st
( ALGO_EXGCD(p,y)`3_3 = 1 implies
( ( ALGO_EXGCD(p,y)`2_3 < 0) implies
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& s = p + z ))
&
( (0 <= ALGO_EXGCD(p,y)`2_3) implies s = ALGO_EXGCD(p,y)`2_3)
)
&
( ALGO_EXGCD(p,y)`3_3 <> 1 implies s = {} ) by A4;
end;
end;
then
consider s be Element of INT such that
A5:
( ALGO_EXGCD(p,y)`3_3 = 1 implies
( ( ALGO_EXGCD(p,y)`2_3 < 0) implies
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& s = p + z ))
&
( (0 <= ALGO_EXGCD(p,y)`2_3) implies s = ALGO_EXGCD(p,y)`2_3)
)
&
( ALGO_EXGCD(p,y)`3_3 <> 1 implies s = {} );
take s;
thus
for y be Element of INT
st y = (x mod p)
holds
( ALGO_EXGCD(p,y)`3_3 = 1 implies
( ( ALGO_EXGCD(p,y)`2_3 < 0) implies
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& s = p + z ))
&
( (0 <= ALGO_EXGCD(p,y)`2_3) implies s = ALGO_EXGCD(p,y)`2_3)
)
&
( ALGO_EXGCD(p,y)`3_3 <> 1 implies s = {} ) by A5;
end;
uniqueness
proof
let s1,s2 be Element of INT;
assume A6:
for y be Element of INT st y = (x mod p) holds
( ALGO_EXGCD(p,y)`3_3 = 1 implies
( ( ALGO_EXGCD(p,y)`2_3 < 0) implies
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3 & s1 = p + z )) &
( (0 <= ALGO_EXGCD(p,y)`2_3) implies s1 = ALGO_EXGCD(p,y)`2_3)) &
( ALGO_EXGCD(p,y)`3_3 <> 1 implies s1 = {} );
assume A7:
for y be Element of INT st y = (x mod p) holds
( ALGO_EXGCD(p,y)`3_3 = 1 implies
( ( ALGO_EXGCD(p,y)`2_3 < 0) implies
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3 & s2 = p + z ))
&
( (0 <= ALGO_EXGCD(p,y)`2_3) implies s2 = ALGO_EXGCD(p,y)`2_3)
)
&
( ALGO_EXGCD(p,y)`3_3 <> 1 implies s2 = {} );
reconsider y = x mod p as Element of INT by INT_1:def 2;
thus s1=s2
proof
per cases;
suppose A8: ALGO_EXGCD(p,y)`3_3 = 1;
thus s1=s2
proof
per cases;
suppose A9: ALGO_EXGCD(p,y)`2_3 < 0;
then
A10: (ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& s1 = p + z ) by A6,A8;
(ex z be Element of INT st z = ALGO_EXGCD(p,y)`2_3
& s2 = p + z ) by A7,A8,A9;
hence s1=s2 by A10;
end;
suppose A11: 0 <= ALGO_EXGCD(p,y)`2_3;
thus
s1 = ALGO_EXGCD(p,y)`2_3 by A11,A8,A6
.=s2 by A11,A8,A7;
end;
end;
end;
suppose A12: ALGO_EXGCD(p,y)`3_3 <> 1;
thus s1= {} by A6,A12
.= s2 by A7,A12;
end;
end;
end;
end;
Lm13:
for x,y,p be Element of INT
st y = x mod p & ALGO_EXGCD(p,y)`3_3 = 1 & p <> 0
holds
( ALGO_INVERSE(x,p) * x ) mod p = 1 mod p
proof
let x,y,p be Element of INT;
assume A1: y = x mod p & ALGO_EXGCD(p,y)`3_3 = 1 & p <> 0;
A2:ALGO_EXGCD(p,y)`3_3 = p gcd y &
ALGO_EXGCD(p,y)`1_3 * p + ALGO_EXGCD(p,y)`2_3 * y
= p gcd y by Th6;
reconsider s1 = ALGO_EXGCD(p,y)`1_3 * p as Integer;
reconsider s2 = (ALGO_EXGCD(p,y))`2_3 * y as Integer;
reconsider s3 = (ALGO_EXGCD(p,y))`2_3 as Integer;
A3:(p mod p)=0 by INT_1:50;
A4: ( ALGO_EXGCD(p,y)`1_3 * p ) mod p
= (( ALGO_EXGCD(p,y)`1_3 mod p ) * (p mod p)) mod p by NAT_D:67
.= 0 by A3,INT_4:12;
reconsider I0 = 0 as Element of INT by INT_1:def 2;
A5: (ALGO_EXGCD(p,y)`1_3 * p + ALGO_EXGCD(p,y)`2_3 * y )
mod p
= ((s1 mod p) + (s2 mod p)) mod p
by NAT_D:66
.= ( ALGO_EXGCD(p,y)`2_3 * y ) mod p by Th1,A4;
per cases;
suppose ALGO_EXGCD(p,y)`2_3 < 0;
then
consider z be Element of INT such that
A6: z = ALGO_EXGCD(p,y)`2_3
& ALGO_INVERSE(x,p) = p + z by Def3,A1;
thus ( ALGO_INVERSE(x,p) * x ) mod p
=( p*x + z*x ) mod p by A6
.= (z*x) mod p by NAT_D:61
.= ((z mod p) *(x mod p)) mod p by NAT_D:67
.= ((z mod p) *((x mod p) mod p) ) mod p by Th1
.= 1 mod p by A5,A6,A2,A1,NAT_D:67;
end;
suppose
0 <= ALGO_EXGCD(p,y)`2_3;
hence
( ALGO_INVERSE(x,p) * x ) mod p
= ((ALGO_EXGCD(p,y)`2_3)*x ) mod p by Def3,A1
.= ((s3 mod p) * (x mod p) ) mod p by NAT_D:67
.= ( (s3 mod p) * ((x mod p) mod p) ) mod p
by Th1
.= 1 mod p by A5,A2,A1,NAT_D:67;
end;
end;
theorem Th7:
for x,p,y be Element of INT
st y = x mod p & ALGO_EXGCD(p,y)`3_3 = 1
holds
( ALGO_INVERSE(x,p) * x ) mod p = 1 mod p
proof
let x,p,y be Element of INT;
assume A1: y = x mod p & ALGO_EXGCD(p,y)`3_3 = 1;
per cases;
suppose A2: p = 0;
thus ( ALGO_INVERSE(x,p) * x ) mod p = 0 by A2,INT_1:def 10
.= 1 mod p by A2,INT_1:def 10;
end;
suppose p <> 0;
hence ( ALGO_INVERSE(x,p) * x ) mod p = 1 mod p by Lm13,A1;
end;
end;
begin ::Algorithm for Chinese Remainder Theorem
:: def ALGO_CRT(nlist):
:: """
:: This function is Chinese Remainder Theorem using Algorithm 2.1.7
:: of C.Pomerance and R.Crandall's book.
::
:: For example:
:: >>> ALGO_CRT([(1,2),(2,3),(3,5)])
:: 23
:: """
:: r = len(nlist)
:: if r == 1 :
:: return nlist [ 0 ] [ 0 ]
::
:: product = []
:: prodinv = []
:: m = 1
:: for i in range(1,r):
:: m = m*nlist[i-1][1]
:: c = inverse(m,nlist[i][1])
:: product.append(m)
:: prodinv.append(c)
::
:: M = product[r-2]*nlist[r-1][1]
:: n = nlist[0][0]
:: for i in range(1,r):
:: u = ((nlist[i][0]-n)*prodinv[i-1]) % nlist[i][1]
:: n += u*product[i-1]
:: return n % M
::==========================================================================================
definition
let nlist be non empty FinSequence of [:INT,INT:];
func ALGO_CRT(nlist) -> Element of INT means
:Def4:
( len nlist = 1 implies it = (nlist.1)`1)
&
( len nlist <> 1 implies
ex m,n,prodc,prodi be FinSequence of INT,
M0,M be Element of INT
st len m = len nlist
& len n = len nlist
& len prodc = len nlist - 1
& len prodi = len nlist - 1
& m.1 =1
& (for i be Nat
st 1<=i & i<=(len m) - 1
holds
ex d,x,y be Element of INT
st x = (nlist.i)`2
&
m.(i+1) = m.i * x
&
y = m.(i+1)
&
d = (nlist.(i+1))`2
&
prodi.i = ALGO_INVERSE(y,d)
&
prodc.i = y
)
& M0 = (nlist.(len m))`2
& M = (prodc.((len m)-1))*M0
& n.1 = (nlist.1)`1
& (for i be Nat st 1<=i & i<=len m - 1 holds
ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(i+1))`1&
u1 = ( nlist.(i+1))`2 &
u = ( (u0-n.i)*(prodi.i)) mod u1 &
n.(i+1) = n.i + u*(prodc.i)) &
it = n.(len m) mod M );
existence
proof
per cases;
suppose A1: len nlist = 1;
then
1 in Seg (len nlist);
then
1 in dom (nlist) by FINSEQ_1:def 3;
then
nlist.1 in [:INT,INT:] by FINSEQ_2:11;
then
(nlist.1)`1 is Element of INT by MCART_1:10;
hence thesis by A1;
end;
suppose A2: len nlist <> 1;
defpred P[Nat,Integer,Integer] means
ex x be Element of INT
st x = (nlist.$1)`2
&
$3 = $2 * x;
reconsider i1=1 as Element of INT by INT_1:def 1;
A3: for n being Nat st 1 <= n & n < (len nlist)
for z being Element of INT ex y being Element of INT st P[n,z,y]
proof
let n being Nat;
assume A4: 1 <= n & n < len nlist;
let z being Element of INT;
n in Seg (len nlist) by A4;
then
n in dom (nlist) by FINSEQ_1:def 3;
then
nlist.n in [:INT,INT:] by FINSEQ_2:11;
then
reconsider x= (nlist.n)`2 as Element of INT by MCART_1:10;
reconsider y= z * x as Element of INT by INT_1:def 2;
take y;
thus P[n,z,y];
end;
consider m being FinSequence of INT such that
A5: len m = len nlist & (m.1 = i1 or len nlist = 0) &
for i be Nat st 1 <= i & i < len nlist
holds P[i,m.i,m.(i+1)]
from RECDEF_1:sch 4(A3);
A6:len m -1 < len m - 0 by XREAL_1:15;
A7:for i be Nat
st 1<=i & i<=(len m) -1
holds ex x be Element of INT
st x = (nlist.i)`2
&
m.(i+1) = m.i * x
proof
let i be Nat;
assume 1<=i & i<=(len m) -1;
then
A8: 1<=i & i< (len nlist) by A5,A6,XXREAL_0:2;
thus ex x be Element of INT
st x = (nlist.i)`2 &
m.(i+1) = m.i * x by A5,A8;
end;
A9: 1 <= (len m) by A5,NAT_1:14;
then
1-1 <= (len m) -1 by XREAL_1:9;
then
reconsider lm = (len m) - 1 as Element of NAT by INT_1:3;
defpred P1[Nat,Integer] means
ex d,x,y be Element of INT
st x = (nlist.$1)`2
&
m.($1+1) = m.$1 * x
&
y = m.($1+1)
&
d = (nlist.($1+1))`2
&
$2 = ALGO_INVERSE(y,d);
A10: for n being Nat st n in Seg lm
ex z being Element of INT st P1[n,z]
proof
let n be Nat;
assume A11: n in Seg lm;
A12: 1 <= n & n <= (len m) - 1 by A11,FINSEQ_1:1;
then
consider x be Element of INT
such that A13: x = (nlist.n)`2
&
m.(n+1) = m.n * x by A7;
reconsider y = m.(n+1) as Element of INT by INT_1:def 2;
n +1 <= (len m) - 1 +1 by A12,XREAL_1:6;
then
1 <= n+1 & n+1 <= len m by NAT_1:12;
then
n+1 in Seg (len nlist) by A5;
then
n+1 in dom (nlist) by FINSEQ_1:def 3;
then
nlist.(n+1) in [:INT,INT:] by FINSEQ_2:11;
then
reconsider d= (nlist.(n+1))`2 as Element of INT
by MCART_1:10;
reconsider w= ALGO_INVERSE(y,d) as Element of INT;
take w;
thus P1[n,w] by A13;
end;
consider prodi being FinSequence of INT such that
A14: dom prodi = Seg lm &
for k be Nat st k in Seg lm holds P1[k,prodi.k]
from FINSEQ_1:sch 5(A10);
A15: len prodi = len nlist - 1 by A5,A14,FINSEQ_1:def 3;
A16:for i be Nat
st 1<=i & i<=(len m) -1
holds ex d,x,y be Element of INT
st x = (nlist.i)`2
&
m.(i+1) = m.i * x
&
y = m.(i+1)
&
d = (nlist.(i+1))`2
&
prodi.i = ALGO_INVERSE(y,d)
proof
let i be Nat;
assume 1<=i & i<=(len m) -1;
then
i in Seg(lm);
hence ex d,x,y be Element of INT st x = (nlist.i)`2
&
m.(i+1) = m.i * x
&
y = m.(i+1)
&
d = (nlist.(i+1))`2
&
prodi.i = ALGO_INVERSE(y,d) by A14;
end;
defpred P2[Nat,Integer] means
ex d,x,y be Element of INT
st x = (nlist.$1)`2 &
m.($1+1) = m.$1 * x &
y = m.($1+1) &
d = (nlist.($1+1))`2 &
prodi.$1 = ALGO_INVERSE(y,d) &
$2 = y;
A17: for n being Nat st n in Seg lm
ex z being Element of INT st P2[n,z]
proof
let n be Nat;
assume A18: n in Seg lm;
1 <= n & n <= (len m) - 1 by A18,FINSEQ_1:1;
then
consider d,x,y be Element of INT such that
A19: x = (nlist.n)`2 &
m.(n+1) = m.n * x &
y = m.(n+1) &
d = (nlist.(n+1))`2 &
prodi.n = ALGO_INVERSE(y,d) by A16;
reconsider w= y as Element of INT;
take w;
thus P2[n,w] by A19;
end;
consider prodc being FinSequence of INT such that
A20: dom prodc = Seg lm &
for k be Nat st k in Seg lm holds P2[k,prodc.k]
from FINSEQ_1:sch 5(A17);
A21: len prodc = len nlist - 1 by A5,A20,FINSEQ_1:def 3;
A22:for i be Nat
st 1<=i & i<=(len m) -1
holds ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m.(i+1) = m.i * x &
y = m.(i+1) &
d = (nlist.(i+1))`2 &
prodi.i = ALGO_INVERSE(y,d) &
prodc.i = y
proof
let i be Nat;
assume 1<=i & i<=(len m) -1;
then
i in Seg(lm);
hence
ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m.(i+1) = m.i * x &
y = m.(i+1) &
d = (nlist.(i+1))`2 &
prodi.i = ALGO_INVERSE(y,d) &
prodc.i = y by A20;
end;
(len nlist) in Seg (len nlist) by FINSEQ_1:3;
then
(len m) in dom (nlist) by A5,FINSEQ_1:def 3;
then
nlist.(len m) in [:INT,INT:] by FINSEQ_2:11;
then
reconsider M0 = (nlist.(len m))`2
as Element of INT by MCART_1:10;
1 < (len m) by A9,A2,A5,XXREAL_0:1;
then
1 + 1 <= (len m) by NAT_1:13;
then
2 -1 <= (len m) -1 by XREAL_1:9;
then
A23: lm in dom (prodc) by A20;
prodc in (INT)* by FINSEQ_1:def 11;
then
reconsider MM = prodc.((len m)-1)
as Element of INT by A23,FINSEQ_1:84;
reconsider M = MM*M0 as Element of INT by INT_1:def 2;
defpred P4[Nat,Integer,Integer ] means
ex u,u0,u1 be Element of INT
st
u0 = ( nlist.($1+1))`1 &
u1 = ( nlist.($1+1))`2 &
u = ( (u0-$2)*(prodi.$1) ) mod u1 &
$3 = $2 + u*(prodc.$1);
reconsider i1=1 as Element of INT by INT_1:def 1;
A24: for n being Nat st 1 <= n & n < (len nlist)
for z being Element
of INT ex y being Element of INT st P4[n,z,y]
proof
let n being Nat;
assume A25: 1 <= n & n < len nlist;
let z being Element of INT;
1 <= n+1 & n+1 <= len m by A25,A5,NAT_1:13;
then
n+1 in Seg (len nlist) by A5;
then
n+1 in dom (nlist) by FINSEQ_1:def 3;
then
A26: nlist.(n+1) in [:INT,INT:] by FINSEQ_2:11;
then
reconsider u0 = ( nlist.(n+1))`1
as Element of INT by MCART_1:10;
reconsider u1= (nlist.(n+1))`2
as Element of INT by A26,MCART_1:10;
reconsider u = (( u0- z)*(prodi.n)) mod u1
as Element of INT by INT_1:def 2;
reconsider y = z + u*(prodc.n)
as Element of INT by INT_1:def 2;
take y;
thus P4[n,z,y];
end;
1 in Seg (len nlist) by A9,A5;
then
1 in dom (nlist) by FINSEQ_1:def 3;
then
nlist.1 in [:INT,INT:] by FINSEQ_2:11;
then
reconsider L1 = (nlist.1)`1 as Element of INT by MCART_1:10;
consider n being FinSequence of INT such that
A27: len n = len nlist & (n.1 = L1 or len nlist = 0) &
for i be Nat st 1 <= i & i < len nlist
holds P4[i,n.i,n.(i+1)] from RECDEF_1:sch 4(A24);
A28:for i be Nat
st 1<=i & i<=(len m) -1
holds
ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(i+1))`1 &
u1 = ( nlist.(i+1))`2 &
u = ( (u0- n.i)*(prodi.i)) mod u1 &
n.(i+1) = n.i + u*(prodc.i)
proof
let i be Nat;
assume 1<=i & i<=(len m) -1;
then
A29: 1<=i & i< (len nlist) by A5,A6,XXREAL_0:2;
thus ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(i+1))`1 &
u1 = ( nlist.(i+1))`2 &
u = ( (u0- n.i)*(prodi.i)) mod u1 &
n.(i+1) = n.i + u*(prodc.i) by A27,A29;
end;
reconsider s = n.(len m) mod M as Element of INT by INT_1:def 2;
M0 = (nlist.(len m))`2
& M = (prodc.((len m)-1))*M0
& s = n.(len m) mod M;
hence thesis by A2,A28,A22,A5,A27,A15,A21;
end;
end;
uniqueness
proof
let s1,s2 be Element of INT;
assume
A30:
( len nlist = 1 implies s1 = (nlist.1)`1)
&
( len nlist <> 1 implies
ex m,n,prodc,prodi be FinSequence of INT,
M0,M be Element of INT
st len m = len nlist
& len n = len nlist
& len prodc = len nlist - 1
& len prodi = len nlist - 1
& m.1 = 1
& (for i be Nat st 1<=i & i<=(len m) -1 holds
ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m.(i+1) = m.i * x &
y = m.(i+1) &
d = (nlist.(i+1))`2 &
prodi.i = ALGO_INVERSE(y,d) &
prodc.i = y
)
& M0 = (nlist.(len m))`2
& M = (prodc.((len m)-1))*M0
& n.1 = (nlist.1)`1
& (for i be Nat
st 1<=i & i<=len m -1
holds
ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(i+1))`1 &
u1 = ( nlist.(i+1))`2 &
u = ( (u0- n.i)*(prodi.i)) mod u1 &
n.(i+1) = n.i + u*(prodc.i))&
s1 = n.(len m) mod M );
assume
A31:
( len nlist = 1 implies s2 = (nlist.1)`1)
&
( len nlist <> 1 implies
ex m,n,prodc,prodi be FinSequence of INT,
M0,M be Element of INT
st len m = len nlist
& len n = len nlist
& len prodc = len nlist - 1
& len prodi = len nlist - 1
& m.1 =1
& (for i be Nat
st 1<=i & i<=(len m) -1
holds
ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m.(i+1) = m.i * x &
y = m.(i+1) &
d = (nlist.(i+1))`2 &
prodi.i = ALGO_INVERSE(y,d) &
prodc.i = y
)
& M0 = (nlist.(len m))`2
& M = (prodc.((len m)-1))*M0
& n.1 = (nlist.1)`1
& (for i be Nat
st 1<=i & i<=len m -1
holds
ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(i+1))`1 &
u1 = ( nlist.(i+1))`2 &
u = ( (u0- n.i)*(prodi.i)) mod u1 &
n.(i+1) = n.i + u*(prodc.i) ) &
s2 = n.(len m) mod M );
per cases;
suppose A32: len nlist = 1;
thus s1 = s2 by A30,A31,A32;
end;
suppose A33: len nlist <> 1;
consider m1,n1,prodc1,prodi1 be FinSequence of INT,
M01,M1 be Element of INT such that
A34: len m1 = len nlist
& len n1 = len nlist
& len prodc1 = len nlist -1
& len prodi1 = len nlist -1
& m1.1 =1
& (for i be Nat
st 1<=i & i<=(len m1) -1
holds
ex d,x,y be Element of INT st x = (nlist.i)`2
&
m1.(i+1) = m1.i * x
&
y = m1.(i+1)
&
d = (nlist.(i+1))`2
&
prodi1.i = ALGO_INVERSE(y,d)
&
prodc1.i = y
)
& M01 = (nlist.(len m1))`2
& M1 = (prodc1.((len m1)-1))*M01
& n1.1 = (nlist.1)`1
& (for i be Nat
st 1<=i & i<=len m1 -1
holds
ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(i+1))`1
&
u1 = ( nlist.(i+1))`2
&
u = ( (u0- n1.i)*(prodi1.i)) mod u1
& n1.(i+1) = n1.i + u*(prodc1.i) )
& s1 = n1.(len m1) mod M1 by A33,A30;
consider m2,n2,prodc2,prodi2 be FinSequence of INT,
M02,M2 be Element of INT such that
A35: len m2 = len nlist
& len n2 = len nlist
& len prodc2 = len nlist -1
& len prodi2 = len nlist -1
& m2.1 =1
& (for i be Nat
st 1<=i & i<=(len m2) -1
holds
ex d,x,y be Element of INT
st x = (nlist.i)`2
&
m2.(i+1) = m2.i * x
&
y = m2.(i+1)
&
d = (nlist.(i+1))`2
&
prodi2.i = ALGO_INVERSE(y,d)
&
prodc2.i = y
)
& M02 = (nlist.(len m2))`2
& M2 = (prodc2.((len m2)-1))*M02
& n2.1 = (nlist.1)`1
& (for i be Nat
st 1<=i & i<=len m2 -1
holds
ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(i+1))`1
&
u1 = ( nlist.(i+1))`2
&
u = ( (u0- n2.i)*(prodi2.i)) mod u1
& n2.(i+1) = n2.i + u*(prodc2.i) )
& s2 = n2.(len m2) mod M2 by A33,A31;
defpred EQ[Nat] means
1<= $1 & $1 <= len m1
implies m1.$1 =m2.$1;
A36:EQ[ 0 ];
A37: for i be Nat
st EQ[i] holds EQ[i+1]
proof
let i be Nat;
assume A38: EQ[i];
assume
1<= i+1 & i+1 <= len m1;
then
A39:1-1 <=i+1 -1 & i+1 -1 <= len m1 -1 by XREAL_1:9;
A40:len m1 -1 <= len m1 - 0 by XREAL_1:13;
per cases;
suppose A41: i = 0;
thus
m1.(i+1) = m2.(i+1) by A34,A35,A41;
end;
suppose A42:i <> 0;
then
A43: 1<=i by NAT_1:14;
A44: ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m1.(i+1) = m1.i * x &
y = m1.(i+1) &
d = (nlist.(i+1))`2 &
prodi1.i = ALGO_INVERSE(y,d) &
prodc1.i = y by A34,A43,A39;
1<=i & i<=len m2 -1 by A42,A39,A34,A35,NAT_1:14;
then ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m2.(i+1) = m2.i * x &
y = m2.(i+1) &
d = (nlist.(i+1))`2 &
prodi2.i = ALGO_INVERSE(y,d) &
prodc2.i = y by A35;
hence
m1.(i+1) = m2.(i+1) by A44,A39,A38,A40,A42,NAT_1:14,XXREAL_0:2;
end;
end;
A45:for k be Nat holds EQ[k]
from NAT_1:sch 2(A36,A37);
A46: now let i be Nat;
assume A47:1<=i & i <=len prodc1;
then
A48: ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m1.(i+1) = m1.i * x &
y = m1.(i+1) &
d = (nlist.(i+1))`2 &
prodi1.i = ALGO_INVERSE(y,d) &
prodc1.i = y by A34;
ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m2.(i+1) = m2.i * x &
y = m2.(i+1) &
d = (nlist.(i+1))`2 &
prodi2.i = ALGO_INVERSE(y,d) &
prodc2.i = y by A35,A47,A34;
hence
prodc1.i = prodc2.i by A48,A34,A35,A45,FINSEQ_1:14;
end;
then
A49: prodc1 = prodc2 by A34,A35;
A50:now let i be Nat;
assume A51:1<=i & i <=len prodi1;
then
A52: ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m1.(i+1) = m1.i * x &
y = m1.(i+1) &
d = (nlist.(i+1))`2 &
prodi1.i = ALGO_INVERSE(y,d) &
prodc1.i = y by A34;
ex d,x,y be Element of INT
st x = (nlist.i)`2 &
m2.(i+1) = m2.i * x &
y = m2.(i+1) &
d = (nlist.(i+1))`2 &
prodi2.i = ALGO_INVERSE(y,d) &
prodc2.i = y by A35,A51,A34;
hence
prodi1.i = prodi2.i by A52,A45,A34,A35,FINSEQ_1:14;
end;
A53: M1 = M2 by A35,A34,A46,FINSEQ_1:14;
defpred EQ[Nat] means
1<= $1 & $1 <= len n1
implies n1.$1 =n2.$1;
A54:EQ[ 0 ];
A55: for k be Nat
st EQ[k] holds EQ[k+1]
proof
let k be Nat;
assume A56: EQ[k];
assume 1<= k+1 & k+1 <= len n1;
then
A57:1-1 <=k+1 -1 & k+1 -1 <= len n1 -1 by XREAL_1:9;
A58:len n1 -1 <= len n1 - 0 by XREAL_1:13;
per cases;
suppose A59: k = 0;
thus
n1.(k+1) = n2.(k+1) by A34,A35,A59;
end;
suppose A60:k <> 0;
then
A61: 1<=k by NAT_1:14;
A62: ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(k+1))`1
&
u1 = ( nlist.(k+1))`2
&
u = ((u0- n1.k)*(prodi1.k)) mod u1
&
n1.(k+1) = n1.k + u*(prodc1.k) by A61,A57,A34;
ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(k+1))`1
&
u1 = ( nlist.(k+1))`2
&
u = ( (u0- n2.k)*(prodi2.k)) mod u1
&
n2.(k+1) = n2.k + u*(prodc2.k) by A61,A57,A34,A35;
hence
n1.(k+1) = n2.(k+1) by A49,A62,A56,A58,A60,A57,A34,A35,A50,FINSEQ_1:14
,NAT_1:14,XXREAL_0:2;
end;
end;
for k be Nat holds EQ[k] from NAT_1:sch 2(A54,A55);
hence s1=s2 by A53,A34,A35,FINSEQ_1:14;
end;
end;
end;
theorem Th8:
for a,b be Element of INT st b <> 0 holds (a mod b),a are_congruent_mod b
proof
let a,b be Element of INT;
assume b <>0;then
A1:a mod b = a - (a div b) * b by INT_1:def 10;
reconsider c = -(a div b) as Element of INT by INT_1:def 2;
take c;
thus thesis by A1;
end;
theorem
for a,b be Element of INT st b <>0 holds
(a mod b ) gcd b = a gcd b by Th8,INT_4:14;
theorem Th10:
for a,b,c be Element of INT
st c <>0 & a = b mod c
&
b,c are_coprime
holds a,c are_coprime
proof
let a,b,c be Element of INT;
assume A1: c <>0 &
a = b mod c
&
b,c are_coprime;
then
b gcd c = 1 by INT_2:def 3;
then
a gcd c = 1 by A1,Th8,INT_4:14;
hence thesis by INT_2:def 3;
end;
Lm14:
for a,b,c be Element of INT
st a = b mod c & c <> 0 holds
ex d be Element of INT st a = b + d * c
proof
let a,b,c be Element of INT;
assume a = b mod c & c <> 0;then
A1:b = (b div c)*c + a by INT_1:59;
reconsider x = -(b div c) as Element of INT by INT_1:def 2;
take x;
thus thesis by A1;
end;
Lm15:
for b,m be FinSequence of INT
st len b = len m
&
(for i be Nat st i in Seg (len b)
holds b.i <> 0 )
&
m.1 = 1
holds
for k be Element of NAT
st
1<= k & k <= len b -1
&
(for i be Nat st 1<=i & i <=k
holds
m.(i+1) = m.i * b.i )
holds
m.(k+1) <> 0
proof
let b,m be FinSequence of INT;
assume len b = len m;
assume A1: (for i be Nat st i in Seg (len b)
holds b.i <> 0 )&
m.1 = 1;
defpred P[Nat] means
( 1<= $1 & $1 <= len b -1
&
(for i be Nat st
1<=i & i <=$1
holds
m.(i+1) = m.i * b.i ) )
implies
m.($1+1) <> 0;
reconsider I0=0 as Element of NAT;
A2:P[0];
A3:for k be Nat st P[k] holds P[k+1]
proof
let k be Nat;
assume A4: P[k];
assume A5:
1<= k+1 & k+1 <= len b -1
&
(for i be Nat st
1<=i & i <=k+1
holds
m.(i+1) = m.i * b.i );
A6: k <= k +1 by NAT_1:12;
per cases;
suppose A7: k = 0;
A8: m.((k+1)+1)
= m.1 * b.1 by A5,A7
.= b.1 by A1;
len b -1 + (0 qua Nat) <= len b - 1 + 1 by XREAL_1:7;
then
k+1 <= len b by A5,XXREAL_0:2;
then
1 <= 1 & 1 <= len b by A5,XXREAL_0:2;
then
1 in Seg(len b);
hence
m.((k+1)+1) <> 0 by A8,A1;
end;
suppose A9:k <> 0;
A10: now let i be Nat;
assume 1<=i & i <=k;
then
1<=i & i <=(k +1) by NAT_1:12;
hence
m.(i+1) = m.i * b.i by A5;
end;
thus
m.((k+1)+1) <> 0
proof
A11:(k+1) +1 <= len b -1 +1 by A5,XREAL_1:6;
A12: (k +1) <= (k+1) +1 by NAT_1:12;
A13: 1<= k+1 by NAT_1:12;
k +1 <= len b by A12,A11,XXREAL_0:2;
then
k+1 in Seg (len b) by A13;
then
A14:
b.(k+1) <> 0 by A1;
m.((k+1)+1) = m.(k+1) * b.(k+1) by A5;
hence
m.((k+1)+1) <> 0 by A14,A10,A4,A5,A6,A9,NAT_1:14,XCMPLX_1:6
,XXREAL_0:2;
end;
end;
end;
for k be Nat holds P[k] from NAT_1:sch 2(A2,A3);
hence thesis;
end;
Lm16:
for b,m be FinSequence of INT
st 2 <=len b
&
(for i,j be Nat st i in Seg (len b)
& j in Seg (len b)
& i <> j
holds b.i,b.j are_coprime )
&
m.1 = 1
holds
for k be Nat
st
1<= k & k <= len b -1
&
(for i be Nat st 1<=i & i <=k
holds
m.(i+1) = m.i * b.i )
holds
for j be Nat st k+1 <= j & j <= len b
holds
m.(k+1),b.j are_coprime
proof
let b,m be FinSequence of INT;
assume 2 <=len b;
assume
A1: (for i,j be Nat st i in Seg (len b)
& j in Seg (len b)
& i <> j
holds b.i,b.j are_coprime )
&
m.1 = 1;
defpred P[Nat] means
( 1<= $1 & $1 <= len b -1
&
(for i be Nat st
1<=i & i <=$1
holds
m.(i+1) = m.i * b.i ) )
implies
for j be Nat st $1+1 <= j & j <= len b
holds
m.($1+1),b.j are_coprime;
reconsider I0=0 as Element of NAT;
A2:P[0];
A3:for k be Nat st P[k] holds P[k+1]
proof
let k be Nat;
assume A4: P[k];
assume A5:
1<= k+1 & k+1 <= len b -1
&
(for i be Nat st 1<=i & i <=k+1 holds
m.(i+1) = m.i * b.i );
A6: k <= k +1 by NAT_1:12;
per cases;
suppose A7: k = 0;
A8: m.((k+1)+1)
= m.1 * b.1 by A5,A7
.= b.1 by A1;
for j be Nat st (k+1)+1 <= j & j <= len b
holds
m.((k+1)+1),b.j are_coprime
proof
let j be Nat;
assume A9:(k+1)+1 <= j & j <= len b;
then
A10: 1 <= j & j <= len b by A7,XXREAL_0:2;
then
A11: j in Seg(len b);
1 <= 1 & 1 <= len b by A10,XXREAL_0:2;
then
A12: 1 in Seg(len b);
1 <> j by A9,A7;
hence
m.((k+1)+1),b.j are_coprime by A8,A1,A11,A12;
end;
hence thesis;
end;
suppose A13:k <> 0;
A14: now let i be Nat;
assume 1<=i & i <=k;
then
1<=i & i <=(k +1) by NAT_1:12;
hence m.(i+1) = m.i * b.i by A5;
end;
thus
for j be Nat st (k+1)+1 <= j & j <= len b
holds
m.((k+1)+1),b.j are_coprime
proof
let j be Nat;
assume A15:(k+1) +1 <= j & j <= len b;
(k +1) <= (k+1) +1 by NAT_1:12;
then
A16: k +1 <= j & j <= len b by A15,XXREAL_0:2;
then
A17: m.(k+1),b.j are_coprime
by A14,A4,A5,A6,A13,NAT_1:14,XXREAL_0:2;
A18: 1<= k+1 by NAT_1:12;
k +1 <= len b by A16,XXREAL_0:2;
then
A19: k+1 in Seg (len b) by A18;
1<=j & j <= len b by A16,A18,XXREAL_0:2;
then
A20: j in Seg (len b);
(k+1) < j by A15,NAT_1:16,XXREAL_0:2;
then
A21:
b.(k+1),b.j are_coprime by A1,A19,A20;
m.((k+1)+1) = m.(k+1) * b.(k+1) by A5;
hence
m.((k+1)+1),b.j are_coprime by A21,A17,INT_2:26;
end;
end;
end;
for k be Nat holds P[k] from NAT_1:sch 2(A2,A3);
hence thesis;
end;
Lm17:
for b,m be FinSequence of INT
st len b = len m
&
m.1 = 1
holds
for k be Element of NAT
st
1<= k & k <= len b -1
&
(for i be Nat st 1<=i & i <=k
holds
m.(i+1) = m.i * b.i )
holds
for j be Nat st 1<= j & j <=k
holds
m.(k+1) mod b.j = 0
proof
let b,m be FinSequence of INT;
assume len b = len m;
assume A1: m.1 = 1;
defpred P[Nat] means
( 1<= $1 & $1 <= len b -1
&
(for i be Nat st
1<=i & i <=$1
holds
m.(i+1) = m.i * b.i ) )
implies
for j be Nat st 1<=j & j <=$1
holds
m.($1+1) mod b.j = 0;
reconsider I0=0 as Element of NAT;
A2:P[0];
A3:for k be Nat st P[k] holds P[k+1]
proof
let k be Nat;
assume A4: P[k];
assume A5:
1<= k+1 & k+1 <= len b -1
&
(for i be Nat st
1<=i & i <=k+1
holds
m.(i+1) = m.i * b.i );
A6: k <= k +1 by NAT_1:12;
per cases;
suppose A7: k = 0;
A8: m.((k+1)+1)
= m.1 * b.1 by A5,A7
.= b.1 by A1;
for j be Nat st 1<= j & j <= (k+1)
holds
m.((k+1)+1) mod b.j =0
proof
let j be Nat;
assume 1<= j & j <=(k+1);
then
j = 1 by A7,XXREAL_0:1;
hence
m.((k+1)+1) mod b.j = 0 by A8,INT_1:50;
end;
hence thesis;
end;
suppose k <> 0;
A9: now let i be Nat;
assume 1<=i & i <=k;
then
1<=i & i <=(k +1) by NAT_1:12;
hence m.(i+1) = m.i * b.i by A5;
end;
thus for j be Nat st 1 <=j & j <= k+1 holds m.((k+1)+1) mod b.j = 0
proof
let j be Nat;
assume A10:1 <=j & j <= k+1;
reconsider bj =b.j as Element of INT by INT_1:def 2;
per cases;
suppose A11: j = k+1;
thus m.((k+1)+1) mod b.j
= (m.(k+1) * b.(k+1)) mod b.j by A5
.= ((m.(k+1) mod b.j ) *( b.(k+1) mod b.j ) )
mod b.j by NAT_D:67
.= ((m.(k+1) mod b.j ) * (0 qua Nat) )
mod b.j by A11,INT_1:50
.= 0 by INT_4:12;
end;
suppose j <> k+1;
then
j < k+1 by A10,XXREAL_0:1;
then
A12: j <= k by NAT_1:13;
thus m.((k+1)+1) mod b.j
= (m.(k+1) * b.(k+1)) mod b.j by A5
.= ((m.(k+1) mod b.j ) *( b.(k+1) mod b.j ) )
mod b.j by NAT_D:67
.= ( 0 *( b.(k+1) mod b.j ) )
mod b.j by A12,A9,A10,A4,A5,A6,XXREAL_0:2
.= 0 by INT_4:12;
end;
end;
end;
end;
for k be Nat holds P[k] from NAT_1:sch 2(A2,A3);
hence thesis;
end;
theorem Th11:
for nlist be non empty FinSequence of [:INT,INT:],
a,b be FinSequence of INT
st len a = len b & len a = len nlist
&
(for i be Nat st i in Seg (len nlist)
holds b.i <> 0 )
&
(for i be Nat st i in Seg (len nlist)
holds
(nlist.i)`1 = a.i & (nlist.i)`2 = b.i )
&
(for i,j be Nat st i in Seg (len nlist)
& j in Seg (len nlist)
& i <> j
holds b.i,b.j are_coprime )
holds
for i be Nat st i in Seg (len nlist)
holds ALGO_CRT(nlist) mod b.i = a.i mod b.i
proof
defpred P[Nat] means
for nlist be non empty FinSequence of [:INT,INT:],
a,b be FinSequence of INT
st len nlist = $1
& len a = len b
& len a = len nlist
& (for i be Nat st i in Seg (len nlist)
holds b.i <> 0 )
&
(for i be Nat st i in Seg (len nlist)
holds
(nlist.i)`1 = a.i & (nlist.i)`2 = b.i )
&
(for i,j be Nat st i in Seg (len nlist)
& j in Seg (len nlist)
& i <> j
holds b.i,b.j are_coprime)
holds
(for i be Nat st i in Seg (len nlist)
holds ALGO_CRT(nlist) mod b.i = a.i mod b.i
);
A1: P[ 0 ];
A2: for n be Nat st P[ n ] holds P[n+1]
proof
let n be Nat;
assume A3:P[n];
let nlist be non empty FinSequence of [:INT,INT:],
a,b be FinSequence of INT;
assume A4: len nlist = n+1
& len a = len b
& len a = len nlist
& (for i be Nat st i in Seg (len nlist)
holds b.i <> 0 )
&
(for i be Nat st i in Seg (len nlist)
holds
(nlist.i)`1 = a.i & (nlist.i)`2 = b.i )
&
(for i,j be Nat st i in Seg (len nlist)
& j in Seg (len nlist)
& i <> j
holds b.i,b.j are_coprime );
per cases;
suppose A5: n = 0;
A6: 1 in Seg(len nlist) by A5,A4;
A7: ALGO_CRT(nlist) = (nlist.1)`1 by Def4,A5,A4
.= a.1 by A4,A6;
thus
for i be Nat st i in Seg (len nlist)
holds ALGO_CRT(nlist) mod b.i = a.i mod b.i
by A7,A5,A4,FINSEQ_1:2,TARSKI:def 1;
end;
suppose A8: n <> 0;
then
A9: 1 <=n by NAT_1:14;
A10: len nlist <> 1 by A4,A8;
reconsider nlist1 = nlist | n
as FinSequence of [:INT,INT:];
reconsider a1 = a | n
as FinSequence of INT;
reconsider b1 = b | n
as FinSequence of INT;
A11: n <= n+1 by NAT_1:11;
then
A12: len a1 = n by A4,FINSEQ_1:59;
A13: len nlist1 = n by A11,A4,FINSEQ_1:59;
then
reconsider nlist1 as non empty FinSequence of [:INT,INT:]
by A8;
A14: dom nlist1 = Seg (len nlist1) by FINSEQ_1:def 3
.= Seg n by A11,A4,FINSEQ_1:59;
n in NAT by ORDINAL1:def 12;
then
A15: len nlist1 = n by A14,FINSEQ_1:def 3;
then
A16: Seg len nlist1 c= Seg (len nlist) by A11,A4,FINSEQ_1:5;
A17: len nlist1 = n
& len a1 = len b1
& len a1 = len nlist1 by A12,A11,A4,FINSEQ_1:59;
A18:for i be Nat st i in Seg (len nlist1)
holds b1.i <> 0
proof
let i be Nat;
assume A19: i in Seg (len nlist1);
then
b1.i =b.i by A15,FUNCT_1:49;
hence thesis by A16,A19,A4;
end;
A20:for i be Nat st i in Seg (len nlist1)
holds
(nlist1.i)`1 = a1.i & (nlist1.i)`2 =b1.i
proof
let i be Nat;
assume A21: i in Seg (len nlist1);
A22:(nlist1.i)`1 = (nlist.i)`1 by A21,A15,FUNCT_1:49
.= a.i by A21,A16,A4
.= a1.i by A21,A15,FUNCT_1:49;
(nlist1.i)`2 = (nlist.i)`2 by A21,A15,FUNCT_1:49
.= b.i by A21,A16,A4
.= b1.i by A21,A15,FUNCT_1:49;
hence thesis by A22;
end;
A23:
for i,j be Nat st i in Seg (len nlist1)
& j in Seg (len nlist1)
& i<>j
holds b1.i,b1.j are_coprime
proof
let i,j be Nat;
assume A24: i in Seg (len nlist1)
& j in Seg (len nlist1)
& i <> j;
A25: b.i = b1.i by A24,A15,FUNCT_1:49;
b.j = b1.j by A24,A15,FUNCT_1:49;
hence thesis by A25,A24,A16,A4;
end;
A26:for i be Nat st i in Seg (len nlist1)
holds ALGO_CRT(nlist1) mod b.i = a.i mod b.i
proof
let i be Nat;
assume A27: i in Seg (len nlist1);
then
a1.i = a.i & b1.i =b.i by A15,FUNCT_1:49;
hence
ALGO_CRT(nlist1) mod b.i = a.i mod b.i by A3,A17,A20,A23,A18,A27;
end;
consider
m,l,prodc,prodi be FinSequence of INT,
M0,M be Element of INT such that
A28:
len m = len nlist
& len l = len nlist
& len prodc = len nlist - 1
& len prodi = len nlist - 1
& m.1 =1
& (for i be Nat
st 1<=i & i<=(len m) - 1
holds
ex d,x,y be Element of INT
st x = (nlist.i)`2
&
m.(i+1) = m.i * x
&
y = m.(i+1)
&
d = (nlist.(i+1))`2
&
prodi.i = ALGO_INVERSE(y,d)
&
prodc.i = y
)
& M0 = (nlist.(len m))`2
& M = (prodc.((len m)-1))*M0
& l.1 = (nlist.1)`1
& (for i be Nat
st 1<=i & i<=len m - 1
holds
ex u,u0,u1 be Element of INT
st
u0 = ( nlist.(i+1))`1
&
u1 = ( nlist.(i+1))`2
&
u = ( (u0- l.i)*(prodi.i) ) mod u1
& l.(i+1) = l.i + u*(prodc.i) )
& ALGO_CRT(nlist) = l.(len m) mod M by A10,Def4;
A29: 1 + 1 <= n + 1 by A9,XREAL_1:6;
reconsider lb1=len b -1 as Nat by A4;
A30:1<= lb1 & lb1 <= lb1 by A4,A8,NAT_1:14;
A31:
for i be Nat st 1<=i & i <=lb1
holds
m.(i+1) = m.i * b.i
proof
let i be Nat;
assume A32: 1<=i & i <=lb1;
then
A33: ex d,x,y be Element of INT
st x = (nlist.i)`2
&
m.(i+1) = m.i * x
&
y = m.(i+1)
&
d = (nlist.(i+1))`2
&
prodi.i = ALGO_INVERSE(y,d)
& prodc.i = y by A4,A28;
i in Seg (len nlist1) by A32,A13,A4;
hence
m.(i+1) = m.i * b.i by A33,A4,A16;
end;
A34:m.(len nlist ),b.(len nlist) are_coprime
by A4,Lm16,A29,A28,A30,A31;
reconsider nn=n as Element of NAT by ORDINAL1:def 12;
set l1 = l | nn, m1 = m | nn;
A35: n <= n+1 by NAT_1:11;
then
A36: len l1 = n by A4,A28,FINSEQ_1:59;
A37: dom m1 = Seg (len m1) by FINSEQ_1:def 3
.= Seg n by A4,A28,A35,FINSEQ_1:59;
A38: len m1 = n by A37,FINSEQ_1:def 3;
1 -1 <=n - 1 by A9,XREAL_1:9;
then
n -1 in NAT by INT_1:3;
then
reconsider nn1 = n-1 as Element of NAT;
reconsider prodi1 = prodi | nn1 as FinSequence of INT;
reconsider prodc1 = prodc | nn1 as FinSequence of INT;
A39: n - 1 <= n - 0 by XREAL_1:10;
then
A40: len prodi1 = nn1 by A4,A28,FINSEQ_1:59;
A41: len prodc1 = nn1 by A39,A4,A28,FINSEQ_1:59;
A42: 1 in Seg n by A9;
A43: l1.1 = l.1 by A42,FUNCT_1:49
.= (nlist1.1)`1 by A42,A28,FUNCT_1:49;
A44: n - 1 <= n - 0 by XREAL_1:10;
A45: now let i be Nat;
assume A46: 1<=i & i<=len m1 - 1;
then
A47: 1<=i & i<=len m1 by A38,A44,XXREAL_0:2;
then
i in Seg (len m1);
hence
m1.i =m.i by A38,FUNCT_1:49;
i in Seg (len l1) by A47,A36,A38;
hence
l1.i =l.i by A36,FUNCT_1:49;
i in Seg (len prodi1) by A46,A38,A40;
hence
prodi1.i =prodi.i by A40,FUNCT_1:49;
i in Seg (len prodc1) by A46,A38,A41;
hence
prodc1.i =prodc.i by A41,FUNCT_1:49;
end;
(len m1) in Seg (len nlist1) by A13,A38,FINSEQ_1:3;
then
A48: (len m1) in Seg (len nlist) by A16;
A49: nlist1.(len m1) = nlist.(len m1) by A13,A38,FINSEQ_1:3,FUNCT_1:49;
(len m1) in dom nlist by A48,FINSEQ_1:def 3;
then
nlist1.(len m1) in [:INT,INT:] by A49,FINSEQ_2:11;
then
reconsider M01 = (nlist1.(len m1))`2 as Element of INT by MCART_1:10;
reconsider M1 = (prodc1.((len m1)-1))*M01
as Element of INT by INT_1:def 2;
A50: len m1 = len nlist1
& len l1 = len nlist1
& len prodc1 = len nlist1 - 1
& len prodi1 = len nlist1 - 1
& m1.1 =1 by A35,A4,A38,A36,A41,A40,A28,A42,FINSEQ_1:59,FUNCT_1:49;
A51: for i be Nat
st 1<=i & i<=(len m1) - 1
holds
ex d,x,y be Element of INT
st x = (nlist1.i)`2
&
m1.(i+1) = m1.i * x
&
y = m1.(i+1)
&
d = (nlist1.(i+1))`2
&
prodi1.i = ALGO_INVERSE(y,d)
&
prodc1.i = y
proof
let i be Nat;
assume A52: 1<=i & i<=(len m1) - 1;
then
A53:m1.i = m.i by A45;
A54:prodi1.i = prodi.i by A45,A52;
A55:prodc1.i = prodc.i by A45,A52;
A56: 1<=i+1 by NAT_1:12;
i+1 <=(len m1) - 1 +1 by A52,XREAL_1:6;
then
A57: i+1 in Seg (len m1) by A56;
then
A58:m1.(i+1) =m.(i+1) by A38,FUNCT_1:49;
A59: 1<=i & i<=len m1 by A52,A38,A44,XXREAL_0:2;
A60: 1<=i & i <= len m - 1 by A28,A4,A52,A38,A44,XXREAL_0:2;
i in Seg (len nlist1) by A38,A13,A59;
then
A61: nlist1.i = nlist.i by A15,FUNCT_1:49;
nlist1.(i+1) = nlist.(i+1) by A38,A57,FUNCT_1:49;
hence thesis by A53,A54,A55,A58,A60,A61,A28;
end;
A62: for i be Nat
st 1<=i & i<=len m1 - 1
holds
ex u,u0,u1 be Element of INT
st
u0 = ( nlist1.(i+1))`1
&
u1 = ( nlist1.(i+1))`2
&
u = ( (u0- l1.i)*(prodi1.i)) mod u1
& l1.(i+1) = l1.i + u*(prodc1.i)
proof
let i be Nat;
assume A63: 1<=i & i<=(len m1) - 1;
then
A64:l1.i = l.i by A45;
A65:prodi1.i = prodi.i by A45,A63;
A66:prodc1.i = prodc.i by A45,A63;
A67: 1<=i+1 by NAT_1:12;
i+1 <=(len m1) - 1 +1 by A63,XREAL_1:6;
then
A68: i+1 in Seg (len m1) by A67;
then
A69:l1.(i+1) =l.(i+1) by A38,FUNCT_1:49;
A70: 1<=i & i <= len m - 1 by A28,A4,A63,A38,A44,XXREAL_0:2;
nlist1.(i+1) = nlist.(i+1) by A38,A68,FUNCT_1:49;
hence thesis by A64,A65,A66,A69,A70,A28;
end;
reconsider s= l1.(len m1) mod M1 as Element of INT by INT_1:def 2;
A71: 1 <= (len m) - 1 by A28,A4,A8,NAT_1:14;
reconsider lm1= (len m) - 1 as Element of NAT by A28;
A72: 1<=lm1 & lm1 <= (len m) - 1 by A28,A4,A8,NAT_1:14;
consider d,x,y be Element of INT such that
A73: x = (nlist.lm1)`2 &
m.(lm1+1) = m.lm1 * x &
y = m.(lm1+1) &
d = (nlist.(lm1+1))`2 &
prodi.lm1 = ALGO_INVERSE(y,d) &
prodc.lm1 = y by A28,A4,A9;
consider u,u0,u1 be Element of INT such that
A74:
u0 = ( nlist.(lm1+1))`1 &
u1 = ( nlist.(lm1+1))`2 &
u = ( (u0-l.lm1)*(prodi.lm1)) mod u1 &
l.(lm1+1) = l.lm1 + u*(prodc.lm1)
by A72,A28;
A75: len nlist in Seg (len nlist) by FINSEQ_1:3;
A76: M0 = b.(len nlist) by A28,A4,A75;
then
A77: M0 <> 0 by A75,A4;
A78:
(u0-l.(len m -1) )* ALGO_INVERSE(y,M0) is Element of INT
by INT_1:def 2;
consider r be Element of INT such that
A79:u = (u0-l.(len m -1) )* ALGO_INVERSE(y,M0)
+ r*M0 by Lm14,A28,A73,A74,A78,A77;
A80: y <> 0 by A73,A28,A4,Lm15,A30,A31;
now per cases;
suppose A81:len nlist1 = 1;
A82: ALGO_CRT(nlist1) = (nlist1.1)`1 by A81,Def4
.= (nlist.1)`1 by A42,FUNCT_1:49
.= l.(len m-1) by A81,A4,A28,A14,FINSEQ_1:def 3;
A83: ALGO_CRT(nlist)
=(l.(len m -1) + u*y ) mod M by A73,A74,A28;
reconsider p=0 as Element of INT by INT_1:def 2;
A84:ALGO_CRT(nlist1) = l.(len m-1) + p * y by A82;
reconsider uy=u*y as Element of INT by INT_1:def 2;
reconsider llm1=l.(len m-1) as Element of INT
by INT_1:def 2;
reconsider ly = llm1 + uy as Element of INT
by INT_1:def 2;
M = y*M0 by A28,A73;
then consider t be Element of INT such that
A85:ALGO_CRT(nlist) =ly + t* M
by Lm14,A83,A77,A80,XCMPLX_1:6;
reconsider qr = r+t as Element of INT by INT_1:def 2;
ALGO_CRT(nlist)
= ALGO_CRT(nlist1) - (llm1* ALGO_INVERSE(y,M0)*y + p*y)
+qr*M0*y + u0* ALGO_INVERSE(y,M0)*y by A28,A73,A79,A85,A82;
hence
ex p,qr be Element of INT st
ALGO_CRT(nlist)
= ALGO_CRT(nlist1)-((l.(len m -1) )*ALGO_INVERSE(y,M0)*y + p*y )
+ qr*M0*y + u0* ALGO_INVERSE(y,M0)*y
& ALGO_CRT(nlist1) = l.(len m-1) + p * y by A84;
end;
suppose A86:len nlist1 <> 1;
then
A87: ALGO_CRT(nlist1) = s by Def4,A50,A51,A62,A43
.= l1.(len m1) mod ((prodc1.((len m1)-1))*M01);
A88: l1.(len l1) =l.(len l1)
by A8,A36,FINSEQ_1:3,FUNCT_1:49
.=l.(len m -1) by A28,A4,A35,FINSEQ_1:59;
2 <= len nlist1 by A86,NAT_1:23;
then
2 - 1 <= len m1 - 1 by A38,A17,XREAL_1:9;
then
A89: 1 <= nn1 & nn1 <= len m1 - 1 by A37,FINSEQ_1:def 3;
A90:M01 = (nlist.(len m1))`2 by A13,A38,FINSEQ_1:3,FUNCT_1:49
.= (nlist.(len m -1 ))`2 by A28,A4,A37,FINSEQ_1:def 3;
consider d1,x1,y1 be Element of INT such that
A91: x1 = (nlist1.nn1)`2 &
m1.(nn1+1) = m1.nn1 * x1 &
y1 = m1.(nn1+1) &
d1 = (nlist1.(nn1+1))`2 &
prodi1.nn1 = ALGO_INVERSE(y1,d1) &
prodc1.nn1 = y1 by A51,A89;
A92:len m1
= len m-1 by A28,A4,A37,FINSEQ_1:def 3;
then
A93:lm1 in Seg (len m1) by A71;
A94:ALGO_CRT(nlist1)
=l.(len m-1) mod (y1*M01)
by A91,A87,A92,A88,A4,A28,A35,FINSEQ_1:59;
A95:
ALGO_CRT(nlist1) is Element of INT
&
l.(len m-1) is Element of INT
&
(y1*M01) is Element of INT by INT_1:def 2;
A96:y =y1 * x by A91,A28,A4,A38,A93,A73,FUNCT_1:49;
then
A97: y1*M01 <> 0 by A28,A4,Lm15,A30,A31,A90,A73;
consider p be Element of INT such that
A98:ALGO_CRT(nlist1) = l.(len m-1) + p* (y1*M01)
by A94,Lm14,A95,A80,A90,A73,A96;
A99: ALGO_CRT(nlist)
= (l.(len m -1) + u*(y1*x) ) mod ((prodc.((len m)-1))*M0)
by A91,A28,A4,A38,A93,A73,A74,FUNCT_1:49
.= (l.(len m -1) + u*(y1*x) )
mod (y1*x*M0) by A91,A28,A4,A38,A93,A73,FUNCT_1:49;
ALGO_CRT(nlist) is Element of INT
&
l.(len m -1) + u*(y1*x) is Element of INT
&
(y1*x*M0) is Element of INT by INT_1:def 2;
then
consider q be Element of INT such that
A100:ALGO_CRT(nlist) = l.(len m -1) + u*(y1*x)
+ q* (y1*x*M0) by A99,Lm14,A90,A73,A97,A77,XCMPLX_1:6;
reconsider qr = r+q as Element of INT by INT_1:def 2;
ALGO_CRT(nlist1)- p* (y1*M01) + u*(y1*x)
= ALGO_CRT(nlist1)- p* (y1*x) + u*(y1*x) by A90,A73
.= ALGO_CRT(nlist1) -((l.(len m -1) )*ALGO_INVERSE(y,M0)*y + p*y )
+ r*M0*y + u0* ALGO_INVERSE(y,M0)*y
by A96,A79;
then ALGO_CRT(nlist)
= ALGO_CRT(nlist1)-((l.(len m -1) )*ALGO_INVERSE(y,M0)*y + p*y )
+ r*M0*y + u0* ALGO_INVERSE(y,M0)*y + q* (y*M0)
by A91,A28,A4,A38,A93,A73,A100,A98,FUNCT_1:49
.= ALGO_CRT(nlist1)-((l.(len m -1) )*ALGO_INVERSE(y,M0)*y + p*y )
+ qr*M0*y + u0* ALGO_INVERSE(y,M0)*y;
hence
ex p,qr be Element of INT st
ALGO_CRT(nlist)
= ALGO_CRT(nlist1)-((l.(len m -1) )*ALGO_INVERSE(y,M0)*y + p*y )
+ qr*M0*y + u0* ALGO_INVERSE(y,M0)*y
&
ALGO_CRT(nlist1) = l.(len m-1) + p * y by A98,A96,A90,A73;
end;
end;
then consider p,qr be Element of INT such that
A101:
ALGO_CRT(nlist)
= ALGO_CRT(nlist1)-((l.(len m -1) )*ALGO_INVERSE(y,M0)*y + p*y )
+ qr*M0*y + u0* ALGO_INVERSE(y,M0)*y
&
ALGO_CRT(nlist1) = l.(len m-1) + p * y;
reconsider y0 = y mod M0 as Element of INT by INT_1:def 2;
y0,M0 are_coprime by A77,Th10,A73,A28,A76,A34;
then
y0 gcd M0 = 1 by INT_2:def 3;
then
A102: ALGO_EXGCD(M0,y0)`3_3 = 1 by Th6;
A103:
((l.(len m -1) )*ALGO_INVERSE(y,M0)*y + p*y )
mod M0
= ((l.(len m -1) )*(ALGO_INVERSE(y,M0)*y) )
mod M0
+ ( p*y mod M0) mod M0 by NAT_D:66
.= (l.(len m -1) mod M0 )*((ALGO_INVERSE(y,M0)*y) mod M0)
mod M0
+ (p*y mod M0) mod M0
by NAT_D:67
.= (l.(len m -1) mod M0 )*(1 mod M0)
mod M0
+ (p*y mod M0) mod M0
by A102,Th7
.= (l.(len m -1) * 1 ) mod M0
+ (p*y mod M0) mod M0
by NAT_D:67
.= ALGO_CRT(nlist1) mod M0 by A101,NAT_D:66;
thus
for i be Nat st i in Seg (len nlist)
holds ALGO_CRT(nlist) mod b.i = a.i mod b.i
proof
let i be Nat;
assume A104: i in Seg (len nlist);
then
A105:1 <= i & i <= len nlist by FINSEQ_1:1;
per cases;
suppose A106: i = len nlist;
A107: b.i <> 0 by A4,A104;
reconsider I0 = 0 as Element of INT by INT_1:def 2;
reconsider K1y = ((l.(len m -1) )*ALGO_INVERSE(y,M0)*y + p*y )
as Element of INT by INT_1:def 2;
reconsider K2y = ((qr)*y)*M0 as Element of INT by INT_1:def 2;
reconsider K3y = u0* (ALGO_INVERSE(y,M0)*y)
as Element of INT by INT_1:def 2;
reconsider K4y = K2y + K3y
as Element of INT by INT_1:def 2;
A108:
K2y mod b.i = (((qr)*y) mod M0) *( M0 mod M0) mod M0
by A76,A106,NAT_D:67
.= ( (( (qr)*y ) mod M0 ) *I0 ) mod M0 by INT_1:50
.= I0 mod b.i by A106,A28,A4,A75;
A109:
K4y mod b.i
= ((I0 mod b.i) + (K3y mod b.i)) mod b.i by A108,NAT_D:66
.= ( I0 + K3y) mod b.i by NAT_D:66
.= ((u0 mod b.i) * ((ALGO_INVERSE(y,M0)*y) mod b.i ))
mod b.i by NAT_D:67
.= ((u0 mod b.i) * (1 mod b.i )) mod b.i
by A102,Th7,A106,A76
.= (u0 * 1 ) mod b.i by NAT_D:67
.= a.i mod b.i by A106,A75,A28,A4,A74;
A110:
(ALGO_CRT(nlist) + (K1y) ) mod b.i
= ((ALGO_CRT(nlist) mod b.i) + (ALGO_CRT(nlist1) mod b.i) )
mod b.i by A103,A106,A76,NAT_D:66
.= (ALGO_CRT(nlist) + ALGO_CRT(nlist1) ) mod b.i by NAT_D:66;
A111:
(ALGO_CRT(nlist1) + (K4y) ) mod b.i
= ((ALGO_CRT(nlist1) mod b.i) + (K4y mod b.i) ) mod b.i by NAT_D:66
.=(ALGO_CRT(nlist1) + a.i ) mod b.i by A109,NAT_D:66;
reconsider LL= (ALGO_CRT(nlist1) + a.i ) mod b.i as Element of INT
by INT_1:def 2;
reconsider LL1= ALGO_CRT(nlist) + ALGO_CRT(nlist1)
as Element of INT by INT_1:def 2;
reconsider bi =b.i
as Element of INT by INT_1:def 2;
consider r be Element of INT such that
A112: LL = LL1 + r *bi
by Lm14,A107,A110,A111,A101;
reconsider LL2= ALGO_CRT(nlist1) + a.i
as Element of INT by INT_1:def 2;
consider s be Element of INT such that
A113: LL = LL2 + s *bi by Lm14,A107;
reconsider LL3= s -r as Element of INT by INT_1:def 2;
A114:
LL3*(b.i) mod b.i = ((LL3 mod b.i) * (b.i mod b.i)) mod b.i
by NAT_D:67
.= ((LL3 mod b.i) * I0 ) mod b.i by INT_1:50
.= I0 mod b.i;
thus
ALGO_CRT(nlist) mod b.i
= (a.i + ((s -r)*(b.i)) ) mod b.i by A112,A113
.= ((a.i mod b.i ) + (I0 mod b.i) ) mod b.i
by A114,NAT_D:66
.= ( a.i + I0 ) mod b.i by NAT_D:66
.= a.i mod b.i;
end;
suppose i <> len nlist;
then
i < len nlist by A105,XXREAL_0:1;
then
i + 1 <= len nlist by NAT_1:13;
then
A115:i + 1 - 1 <= len nlist -1 by XREAL_1:9;
then
A116: 1<= i & i <= len nlist1 by A35,A4,A104,FINSEQ_1:1,59;
A117:i in Seg (len nlist1) by A115,A4,A17,A105;
reconsider K1 = (l.(len m -1) )*ALGO_INVERSE(y,M0) + p
as Element of INT by INT_1:def 2;
reconsider K2 = (qr)*M0 + u0* ALGO_INVERSE(y,M0)
as Element of INT by INT_1:def 2;
reconsider I0 = 0 as Element of INT by INT_1:def 2;
A118: y mod b.i = 0 by A17,A73,Lm17,A30,A31,A4,A28,A116;
reconsider K1y = K1*y as Element of INT by INT_1:def 2;
reconsider K2y = K2*y as Element of INT by INT_1:def 2;
A119:
(K1* y) mod b.i = (K1 mod b.i) *(y mod b.i) mod b.i by NAT_D:67
.= 0 mod b.i by A118;
A120:
(K2* y) mod b.i = (K2 mod b.i) *(y mod b.i) mod b.i by NAT_D:67
.= 0 mod b.i by A118;
A121:
(ALGO_CRT(nlist) + (K1y) ) mod b.i
= ((ALGO_CRT(nlist) mod b.i) + (K1y mod b.i) ) mod b.i by NAT_D:66
.=(ALGO_CRT(nlist) + I0 ) mod b.i by A119,NAT_D:66
.=ALGO_CRT(nlist) mod b.i;
(ALGO_CRT(nlist1) + (K2y) ) mod b.i
= ((ALGO_CRT(nlist1) mod b.i) + (K2y mod b.i) ) mod b.i by NAT_D:66
.=(ALGO_CRT(nlist1) + I0 ) mod b.i by A120,NAT_D:66
.=ALGO_CRT(nlist1) mod b.i;
hence
ALGO_CRT(nlist) mod b.i = a.i mod b.i by A117,A101,A121,A26;
end;
end;
end;
end;
for n be Nat holds P[n] from NAT_1:sch 2(A1,A2);
hence thesis;
end;
Lm18:
for x,y,a,b be Element of INT
st x mod a = y mod a
& x mod b = y mod b
& a,b are_coprime
holds
x mod (a*b) = y mod (a*b)
proof
let x,y,a,b be Element of INT;
assume
A1: x mod a = y mod a
& x mod b = y mod b
& a,b are_coprime;
set g1 = x mod a;
set g2 = x mod b;
per cases;
suppose A2: a*b = 0;
thus
x mod (a*b)
=0 by A2,INT_1:def 10
.= y mod (a*b) by A2,INT_1:def 10;
end;
suppose a*b <> 0;
then
A3: a <> 0 & b <> 0;
A4: y = (y div a)*a + (y mod a) by A3,INT_1:59;
A5: x = (x div b)*b + (x mod b) by A3,INT_1:59;
x-y = (x div a)*a + (x mod a)
- ((y div a)*a + (y mod a)) by A3,A4,INT_1:59
.= ((x div a) - (y div a)) *a by A1;
then
a divides x-y;
then
A6: x,y are_congruent_mod a;
x-y = (x div b)*b + (x mod b)
- ((y div b)*b + (y mod b)) by A3,A5,INT_1:59
.= ((x div b) - (y div b)) *b by A1;
then
b divides x-y;
then
x,y are_congruent_mod b;
then
x,y are_congruent_mod (a*b)
by A1,A6,INT_6:21;
then
(a*b) divides x-y;
then
consider p be Integer
such that A7: x-y = (a*b)*p;
reconsider I0 =0 as Element of INT by INT_1:def 2;
thus
x mod (a*b) = (y + (a*b)*p ) mod (a*b) by A7
.= ( (y mod (a*b)) + ( ((a*b)*p) mod (a*b) ) ) mod (a*b)
by NAT_D:66
.= ((y mod (a*b))
+ (( ((a*b) mod (a*b)) * (p mod (a*b)) ) mod (a*b) ))
mod (a*b) by NAT_D:67
.= ((y mod (a*b)) + (( I0* (p mod (a*b)) ) mod (a*b)) )
mod (a*b) by INT_1:50
.= ((y + I0)) mod (a*b) by NAT_D:66
.= y mod (a*b);
end;
end;
theorem Th12:
for x,y be Element of INT,
b,m be non empty FinSequence of INT
st
2 <=len b
&
(for i,j be Nat st i in Seg (len b)
& j in Seg (len b)
& i <> j
holds b.i,b.j are_coprime )
&
(for i be Nat
st i in Seg len b
holds x mod b.i = y mod b.i )
&
m.1 = 1 holds
for k be Element of NAT
st
1<= k & k <= len b
&
(for i be Nat st 1<=i & i <=k
holds
m.(i+1) = m.i * b.i )
holds
x mod m.(k+1) = y mod m.(k+1)
proof
let x,y be Element of INT,
b,m be non empty FinSequence of INT;
assume
A1: 2 <=len b;
assume
A2:
for i,j be Nat st i in Seg (len b)
& j in Seg (len b)
& i <> j
holds b.i,b.j are_coprime;
assume
A3:
for i be Nat
st i in Seg len b
holds x mod b.i = y mod b.i;
assume
A4:
m.1 = 1;
defpred P[Nat] means
( 1<= $1 & $1 <= len b
&
(for i be Nat st 1<=i & i <=$1
holds
m.(i+1) = m.i * b.i ) )
implies
x mod m.($1+1) = y mod m.($1+1);
reconsider I0=0 as Element of NAT;
A5:P[0];
A6:for k be Nat st P[k] holds P[k+1]
proof
let k be Nat;
assume A7: P[k];
assume A8:
1<= k+1 & k+1 <= len b
&
(for i be Nat st
1<=i & i <=k+1
holds
m.(i+1) = m.i * b.i );
A9: k <= k +1 by NAT_1:12;
per cases;
suppose A10: k = 0;
A11: m.((k+1)+1)
= m.1 * b.1 by A8,A10
.= b.1 by A4;
1<= 1 & 1<= len b by NAT_1:14;
then
A12: 1 in Seg len b;
thus
x mod m.((k+1)+1)
= y mod m.((k+1)+1) by A11,A12,A3;
end;
suppose A13:k <> 0;
k+1 -1 <= len b -1 by A8,XREAL_1:9;
then
A14: 1<=k & k <= len b -1 by A13,NAT_1:14;
A15: now let i be Nat;
assume 1<=i & i <=k;
then
1<=i & i <=(k +1) by NAT_1:12;
hence
m.(i+1) = m.i * b.i by A8;
end;
A16: m.((k+1)+1) = m.(k+1) * b.(k+1) by A8;
k+1 in Seg len b by A8;
then
A17: x mod b.(k+1) = y mod b.(k+1) by A3;
A18: m.(k+1),b.(k+1) are_coprime
by Lm16,A15,A14,A1,A2,A4,A8;
m.(k+1) is Element of INT & b.(k+1) is Element of INT
by INT_1:def 2;
hence
x mod m.((k+1)+1) = y mod m.((k+1)+1)
by A16,A17,A7,A13,A8,A9,A15,A18,Lm18,NAT_1:14,XXREAL_0:2;
end;
end;
for k be Nat holds P[k] from NAT_1:sch 2(A5,A6);
hence thesis;
end;
theorem Th13:
for b be FinSequence of INT
st len b = 1 holds Product b = b.1
proof
let b be FinSequence of INT;
assume len b = 1;
then
b = <*b.1*> by FINSEQ_1:40;
hence Product b = b.1 by RVSUM_1:95;
end;
theorem Th14:
for b be FinSequence of INT
ex m be non empty FinSequence of INT
st
len m = len b + 1
&
m.1 = 1
&
(for i be Nat st 1<=i & i <=len b
holds
m.(i+1) = m.i * b.i )
&
Product b = m.(len b + 1 )
proof
defpred P[Nat]
means
for b be FinSequence of INT
st
len b = $1
holds
ex m be non empty FinSequence of INT
st
( len m = len b + 1
&
m.1 = 1
&
(for i be Nat st 1<=i & i <=len b
holds
m.(i+1) = m.i * b.i ) )
& Product b = m.(len b + 1);
A1: P[0]
proof
let b be FinSequence of INT;
assume A2:len b = 0;
A3: 1 in INT by INT_1:def 2;
rng (<*(1 qua Integer ) *>) = {(1 qua Integer)} by FINSEQ_1:39;
then
rng (<*(1 qua Integer ) *>) c= INT
by A3,ZFMISC_1:31;
then
reconsider m=<*(1 qua Integer ) *>
as non empty FinSequence of INT by FINSEQ_1:def 4;
A4: len m = len b + 1 by A2,FINSEQ_1:40;
A5: m.1 = 1 by FINSEQ_1:40;
A6: for i be Nat st 1<=i & i <=len b
holds
m.(i+1) = m.i * b.i by A2;
b = <*>REAL by A2;
hence thesis by A4,A5,A6,RVSUM_1:94;
end;
A7: for k be Nat st P[k] holds P[k+1]
proof
let k be Nat;
assume A8: P[k];
let b be FinSequence of INT;
assume A9: len b = k+1;
set b1 = b | k;
A10: len b1 = k by A9,FINSEQ_1:59,NAT_1:12;
then
consider m1 be non empty FinSequence of INT such that
A11:
(
len b1 + 1 = len m1
&
m1.1 = 1
&
(for i be Nat st 1<=i & i <=len b1
holds
m1.(i+1) = m1.i * b1.i ) )
& Product b1 = m1.(len b1+1) by A8;
set m = m1 ^ <* (Product b1)*b.(len b) *>;
A12: (Product b1)*b.(len b) in INT by A11,INT_1:def 2;
A13: rng (<*(Product b1)*b.(len b) *>)
= {(Product b1)*b.(len b)} by FINSEQ_1:39;
then
A14: rng (<* (Product b1)*b.(len b) *>) c= INT
by A12,ZFMISC_1:31;
A15: len m = len m1 + len (<* (Product b1)*b.(len b) *>)
by FINSEQ_1:22
.= (len b1 + 1) + 1 by A11,FINSEQ_1:40
.= len b + 1 by A9,FINSEQ_1:59,NAT_1:12;
A16: rng m = rng m1 \/ {(Product b1)*b.(len b)}
by A13,FINSEQ_1:31;
rng m1 c= INT by FINSEQ_1:def 4;
then
rng m c= INT by A13,A16,A14,XBOOLE_1:8;
then
reconsider m as non empty FinSequence of INT by FINSEQ_1:def 4;
A17: len m1 = len b1 + 1 by A11
.= k + 1 by A9,FINSEQ_1:59,NAT_1:12;
1 <= 1 & 1 <=k+1 by NAT_1:12;
then
1 in Seg (len m1) by A17;
then
1 in dom m1 by FINSEQ_1:def 3;
then
A18: m.1 =1 by A11,FINSEQ_1:def 7;
A19:for i be Nat st 1<=i & i <=len b
holds
m.(i+1) = m.i * b.i
proof
let i be Nat;
assume A20: 1<=i & i <=len b;
per cases;
suppose A21: i = len b;
len b1+1 in Seg (len m1) by A10,A17,FINSEQ_1:4;
then
len b1+1 in dom m1 by FINSEQ_1:def 3;
then
A22: m1.(len b1+1) = m.(len b1+1) by FINSEQ_1:def 7
.= m.i by A9,A21,FINSEQ_1:59,NAT_1:12;
1 in Seg 1;
then
A23: 1 in dom (<* (Product b1)*b.(len b) *>)
by FINSEQ_1:38;
thus m.(i+1) = (<* (Product b1)*b.(len b) *>).1
by A21,A9,A17,A23,FINSEQ_1:def 7
.= m.i * b.i by A22,A21,A11,FINSEQ_1:40;
end;
suppose i <> len b;
then
A24: i < len b by A20,XXREAL_0:1;
then
A25: 1<=i & i <=len b1 by A10,A9,A20,NAT_1:13;
then A26: m1.(i+1) = m1.i * b1.i by A11;
i in Seg(len m1) by A20,A9,A17;
then
A27: i in dom m1 by FINSEQ_1:def 3;
A28:i +1 <= len m1 by A9,A17,A24,NAT_1:13;
1 <= i + 1 by NAT_1:12;
then
i+1 in Seg(len m1) by A28;
then
A29: i+1 in dom m1 by FINSEQ_1:def 3;
i in Seg k by A25,A10;
then
A30: b.i = b1.i by FUNCT_1:49;
A31: m.i = m1.i by A27,FINSEQ_1:def 7;
thus m.(i+1) = m.i * b.i by A26,A29,A30,A31,FINSEQ_1:def 7;
end;
end;
b|(k+1)=b1 ^ <*b.(len b)*> by A9,INT_6:5; then
A32: b = b1^<* b.(len b )*> by A9,FINSEQ_1:58;
len b in Seg (len m1) by A9,A17,FINSEQ_1:4; then
A33: len b in dom m1 by FINSEQ_1:def 3;
A34: 1<=len b & len b <=len b by A9,NAT_1:12;
Product b
= m1.(len b1+1)*b.(len b ) by A11,A32,RVSUM_1:96
.= m1.(len b )*b.(len b ) by A9,FINSEQ_1:59,NAT_1:12
.= m.(len b)*b.(len b ) by A33,FINSEQ_1:def 7
.= m.(len b + 1) by A19,A34;
hence thesis by A15,A18,A19;
end;
for k be Nat holds P[k] from NAT_1: sch 2(A1,A7);
hence thesis;
end;
theorem
for nlist be non empty FinSequence of [:INT,INT:],
a,b be non empty FinSequence of INT,
x,y be Element of INT
st len a = len b & len a = len nlist
&
(for i be Nat st i in Seg (len nlist)
holds b.i <> 0 )
&
(for i be Nat st i in Seg (len nlist)
holds
(nlist.i)`1 = a.i & (nlist.i)`2 =b.i )
&
(for i,j be Nat st i in Seg (len nlist)
& j in Seg (len nlist)
& i <> j
holds b.i,b.j are_coprime )
&
(for i be Nat st i in Seg (len nlist)
holds x mod b.i = a.i mod b.i )
& y = Product b
holds ALGO_CRT(nlist) mod y = x mod y
proof
let nlist be non empty FinSequence of [:INT,INT:],
a,b be non empty FinSequence of INT,
x,y be Element of INT;
assume A1:
len a = len b & len a = len nlist;
assume A2:
for i be Nat st i in Seg (len nlist)
holds b.i <> 0;
assume A3:
for i be Nat st i in Seg (len nlist)
holds
(nlist.i)`1 = a.i & (nlist.i)`2 = b.i;
assume A4:
for i,j be Nat st i in Seg (len nlist)
& j in Seg (len nlist)
& i <> j
holds b.i,b.j are_coprime;
assume A5:
for i be Nat st i in Seg (len nlist)
holds x mod b.i = a.i mod b.i;
assume A6: y = Product b;
A7: for i be Nat st i in Seg (len nlist)
holds ALGO_CRT(nlist) mod b.i = x mod b.i
proof
let i be Nat;
assume A8: i in Seg (len nlist);
hence ALGO_CRT(nlist) mod b.i = a.i mod b.i by Th11,A1,A2,A3,A4
.= x mod b.i by A5,A8;
end;
per cases;
suppose A9: len nlist = 1;
then
A10: 1 in Seg(len nlist);
thus
ALGO_CRT(nlist) mod y
= ALGO_CRT(nlist) mod b.1 by A9,A1,Th13,A6
.= x mod b.1 by A7,A10
.= x mod y by A9,A1,Th13,A6;
end;
suppose A11: len nlist <> 1;
A12: 2 <= len nlist by A11,NAT_1:23;
A13: 2 <= len b by A1,A11,NAT_1:23;
consider m be non empty FinSequence of INT such that
A14:
len m = len b + 1 & m.1 = 1 &
(for i be Nat st 1<=i & i <=len b holds
m.(i+1) = m.i * b.i ) &
Product b = m.(len b + 1) by Th14;
1<= len b & len b <= len b by A13,XXREAL_0:2;
hence ALGO_CRT(nlist) mod y = x mod y by A6,A14,Th12,A1,A4,A7,A12;
end;
end;