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:: Basic Algebraic Structures
::  by Library Committee

environ

 vocabularies XBOOLE_0, SUBSET_1, BINOP_1, ZFMISC_1, STRUCT_0, ARYTM_3,
      FUNCT_1, FUNCT_5, SUPINF_2, ARYTM_1, RELAT_1, MESFUNC1, ALGSTR_0, CARD_1;
 notations TARSKI, XBOOLE_0, SUBSET_1, ZFMISC_1, BINOP_1, FUNCT_5, ORDINAL1,
      CARD_1, STRUCT_0;
 constructors BINOP_1, STRUCT_0, ZFMISC_1, FUNCT_5;
 registrations ZFMISC_1, CARD_1, STRUCT_0;
 theorems STRUCT_0;

begin :: Additive structures

reserve D for non empty set,
  d,e for Element of D,
  o,o1 for BinOp of D;
reserve T for trivial set,
  s,t for Element of T,
  f,f1 for BinOp of T;
reserve N for non trivial set,
  n,m for Element of N,
  b,b1 for BinOp of N;

definition
  struct (1-sorted) addMagma (# carrier -> set, addF -> BinOp of the carrier
  #);
end;

registration
  let D,o;
  cluster addMagma(#D,o#) -> non empty;
  coherence;
end;

registration
  let T,f;
  cluster addMagma(#T,f#) -> trivial;
  coherence;
end;

registration
  let N,b;
  cluster addMagma(#N,b#) -> non trivial;
  coherence;
end;

definition
  let M be addMagma;
  let x,y be Element of M;
  func x+y -> Element of M equals
  (the addF of M).(x,y);
  coherence;
end;

definition
  func Trivial-addMagma -> addMagma equals
  addMagma(#{0}, op2 #);
  coherence;
end;

registration
  cluster Trivial-addMagma -> 1-element strict;
  coherence;
end;

registration
  cluster strict 1-element for addMagma;
  existence
  proof
    take Trivial-addMagma;
    thus thesis;
  end;
end;

definition
  let M be addMagma, x be Element of M;
  attr x is left_add-cancelable means
  for y,z being Element of M st x+y = x+z holds y = z;
  attr x is right_add-cancelable means

  for y,z being Element of M st y+ x = z+x holds y = z;
end;

definition
  let M be addMagma, x be Element of M;
  attr x is add-cancelable means

  x is right_add-cancelable left_add-cancelable;
end;

registration
  let M be addMagma;
  cluster right_add-cancelable left_add-cancelable -> add-cancelable for
Element
    of M;
  coherence;
  cluster add-cancelable -> right_add-cancelable left_add-cancelable for
Element
    of M;
  coherence;
end;

definition
  let M be addMagma;
  attr M is left_add-cancelable means
  :Def6:
  for x being Element of M holds x is left_add-cancelable;
  attr M is right_add-cancelable means
  :Def7:
  for x being Element of M holds x is right_add-cancelable;
end;

definition
  let M be addMagma;
  attr M is add-cancelable means

  M is right_add-cancelable left_add-cancelable;
end;

registration
  cluster right_add-cancelable left_add-cancelable -> add-cancelable for
addMagma;
  coherence;
  cluster add-cancelable -> right_add-cancelable left_add-cancelable for
addMagma;
  coherence;
end;

registration
  cluster Trivial-addMagma -> add-cancelable;
  coherence
  proof
    set M = Trivial-addMagma;
    thus M is right_add-cancelable
    proof
      let x,y,z be Element of M;
      assume y+x = z+x;
      thus thesis by STRUCT_0:def 10;
    end;
    let x,y,z being Element of M;
    assume x+y = x+z;
    thus thesis by STRUCT_0:def 10;
  end;
end;

registration
  cluster add-cancelable strict 1-element for addMagma;
  existence
  proof
    take Trivial-addMagma;
    thus thesis;
  end;
end;

registration
  let M be left_add-cancelable addMagma;
  cluster -> left_add-cancelable for Element of M;
  coherence by Def6;
end;

registration
  let M be right_add-cancelable addMagma;
  cluster -> right_add-cancelable for Element of M;
  coherence by Def7;
end;

definition
  struct (ZeroStr,addMagma) addLoopStr (# carrier -> set, addF -> BinOp of the
    carrier, ZeroF -> Element of the carrier #);
end;

registration
  let D,o,d;
  cluster addLoopStr(#D,o,d#) -> non empty;
  coherence;
end;

registration
  let T,f,t;
  cluster addLoopStr(#T,f,t#) -> trivial;
  coherence;
end;

registration
  let N,b,m;
  cluster addLoopStr(#N,b,m#) -> non trivial;
  coherence;
end;

definition
  func Trivial-addLoopStr -> addLoopStr equals
  addLoopStr(#{0}, op2, op0 #);
  coherence;
end;

registration
  cluster Trivial-addLoopStr -> 1-element strict;
  coherence;
end;

registration
  cluster strict 1-element for addLoopStr;
  existence
  proof
    take Trivial-addLoopStr;
    thus thesis;
  end;
end;

definition
  let M be addLoopStr, x be Element of M;
  attr x is left_complementable means

  ex y being Element of M st y+x = 0.M;
  attr x is right_complementable means
  ex y being Element of M st x+y = 0.M;
end;

definition
  let M be addLoopStr, x be Element of M;
  attr x is complementable means

  x is right_complementable left_complementable;
end;

registration
  let M be addLoopStr;
  cluster right_complementable left_complementable -> complementable for
Element
    of M;
  coherence;
  cluster complementable -> right_complementable left_complementable for
Element
    of M;
  coherence;
end;

definition
  let M be addLoopStr, x be Element of M;
  assume
A1: x is left_complementable right_add-cancelable;
  func -x -> Element of M means
  it + x = 0.M;
  existence by A1;
  uniqueness by A1;
end;

definition
  let V be addLoopStr;
  let v,w be Element of V;
  func v - w -> Element of V equals
  v + -w;
  correctness;
end;

registration
  cluster Trivial-addLoopStr -> add-cancelable;
  coherence
  proof
    set M = Trivial-addLoopStr;
    thus M is right_add-cancelable
    proof
      let x,y,z be Element of M;
      assume y+x = z+x;
      thus thesis by STRUCT_0:def 10;
    end;
    let x,y,z being Element of M;
    assume x+y = x+z;
    thus thesis by STRUCT_0:def 10;
  end;
end;

definition
  let M be addLoopStr;
  attr M is left_complementable means
  :Def15:
  for x being Element of M holds x is left_complementable;
  attr M is right_complementable means
  :Def16:
  for x being Element of M holds x is right_complementable;
end;

definition
  let M be addLoopStr;
  attr M is complementable means

  M is right_complementable left_complementable;
end;

registration
  cluster right_complementable left_complementable -> complementable
    for addLoopStr;
  coherence;
  cluster complementable -> right_complementable left_complementable
    for addLoopStr;
  coherence;
end;

registration
  cluster Trivial-addLoopStr -> complementable;
  coherence
  proof
    set M = Trivial-addLoopStr;
    thus M is right_complementable
    proof
      let x be Element of M;
      take x;
      thus thesis by STRUCT_0:def 10;
    end;
    let x being Element of M;
    take x;
    thus thesis by STRUCT_0:def 10;
  end;
end;

registration
  cluster complementable add-cancelable strict 1-element for addLoopStr;
  existence
  proof
    take Trivial-addLoopStr;
    thus thesis;
  end;
end;

registration
  let M be left_complementable addLoopStr;
  cluster -> left_complementable for Element of M;
  coherence by Def15;
end;

registration
  let M be right_complementable addLoopStr;
  cluster -> right_complementable for Element of M;
  coherence by Def16;
end;

begin :: Multiplicative structures

definition
  struct (1-sorted) multMagma (# carrier -> set, multF -> BinOp of the carrier
  #);
end;

registration
  let D,o;
  cluster multMagma(#D,o#) -> non empty;
  coherence;
end;

registration
  let T,f;
  cluster multMagma(#T,f#) -> trivial;
  coherence;
end;

registration
  let N,b;
  cluster multMagma(#N,b#) -> non trivial;
  coherence;
end;

definition
  let M be multMagma;
  let x,y be Element of M;
  func x*y -> Element of M equals
  (the multF of M).(x,y);
  coherence;
end;

definition
  func Trivial-multMagma -> multMagma equals
  multMagma(#{0}, op2 #);
  coherence;
end;

registration
  cluster Trivial-multMagma -> 1-element strict;
  coherence;
end;

registration
  cluster strict 1-element for multMagma;
  existence
  proof
    take Trivial-multMagma;
    thus thesis;
  end;
end;

definition
  let M be multMagma, x be Element of M;
  attr x is left_mult-cancelable means
  for y,z being Element of M st x*y = x*z holds y = z;
  attr x is right_mult-cancelable means

  for y,z being Element of M st y*x = z*x holds y = z;
end;

definition
  let M be multMagma, x be Element of M;
  attr x is mult-cancelable means

  x is right_mult-cancelable left_mult-cancelable;
end;

registration
  let M be multMagma;
  cluster right_mult-cancelable left_mult-cancelable -> mult-cancelable
    for Element of M;
  coherence;
  cluster mult-cancelable -> right_mult-cancelable left_mult-cancelable
    for Element of M;
  coherence;
end;

definition
  let M be multMagma;
  attr M is left_mult-cancelable means
  :Def23:
  for x being Element of M holds x is left_mult-cancelable;
  attr M is right_mult-cancelable means
  :Def24:
  for x being Element of M holds x is right_mult-cancelable;
end;

definition
  let M be multMagma;
  attr M is mult-cancelable means

  M is left_mult-cancelable right_mult-cancelable;
end;

registration
  cluster right_mult-cancelable left_mult-cancelable -> mult-cancelable
    for multMagma;
  coherence;
  cluster mult-cancelable -> right_mult-cancelable left_mult-cancelable
    for multMagma;
  coherence;
end;

registration
  cluster Trivial-multMagma -> mult-cancelable;
  coherence
  proof
    set M = Trivial-multMagma;
    thus M is left_mult-cancelable
    proof
      let x,y,z be Element of M;
      assume x*y = x*z;
      thus thesis by STRUCT_0:def 10;
    end;
    let x,y,z being Element of M;
    assume y*x = z*x;
    thus thesis by STRUCT_0:def 10;
  end;
end;

registration
  cluster mult-cancelable strict 1-element for multMagma;
  existence
  proof
    take Trivial-multMagma;
    thus thesis;
  end;
end;

registration
  let M be left_mult-cancelable multMagma;
  cluster -> left_mult-cancelable for Element of M;
  coherence by Def23;
end;

registration
  let M be right_mult-cancelable multMagma;
  cluster -> right_mult-cancelable for Element of M;
  coherence by Def24;
end;

definition
  struct (OneStr,multMagma) multLoopStr (# carrier -> set, multF -> BinOp of
    the carrier, OneF -> Element of the carrier #);
end;

registration
  let D,o,d;
  cluster multLoopStr(#D,o,d#) -> non empty;
  coherence;
end;

registration
  let T,f,t;
  cluster multLoopStr(#T,f,t#) -> trivial;
  coherence;
end;

registration
  let N,b,m;
  cluster multLoopStr(#N,b,m#) -> non trivial;
  coherence;
end;

definition
  func Trivial-multLoopStr -> multLoopStr equals
  multLoopStr(#{0}, op2, op0 #);
  coherence;
end;

registration
  cluster Trivial-multLoopStr -> 1-element strict;
  coherence;
end;

registration
  cluster strict 1-element for multLoopStr;
  existence
  proof
    take Trivial-multLoopStr;
    thus thesis;
  end;
end;

registration
  cluster Trivial-multLoopStr -> mult-cancelable;
  coherence
  proof
    set M = Trivial-multLoopStr;
    thus M is left_mult-cancelable
    proof
      let x,y,z be Element of M;
      assume x*y = x*z;
      thus thesis by STRUCT_0:def 10;
    end;
    let x,y,z being Element of M;
    assume y*x = z*x;
    thus thesis by STRUCT_0:def 10;
  end;
end;

definition
  let M be multLoopStr, x be Element of M;
  attr x is left_invertible means

  ex y being Element of M st y*x = 1.M;
  attr x is right_invertible means
  ex y being Element of M st x*y = 1.M;
end;

definition
  let M be multLoopStr, x be Element of M;
  attr x is invertible means
  x is right_invertible left_invertible;
end;

registration
  let M be multLoopStr;
  cluster right_invertible left_invertible -> invertible for Element of M;
  coherence;
  cluster invertible -> right_invertible left_invertible for Element of M;
  coherence;
end;

definition
  let M be multLoopStr, x be Element of M;
  assume that
A1: x is left_invertible and
A2: x is right_mult-cancelable;
  func /x -> Element of M means
  it * x = 1.M;
  existence by A1;
  uniqueness by A2;
end;

definition
  let M be multLoopStr;
  attr M is left_invertible means
  :Def31:
  for x being Element of M holds x is left_invertible;
  attr M is right_invertible means
  :Def32:
  for x being Element of M holds x is right_invertible;
end;

definition
  let M be multLoopStr;
  attr M is invertible means

  M is right_invertible left_invertible;
end;

registration
  cluster right_invertible left_invertible -> invertible for multLoopStr;
  coherence;
  cluster invertible -> right_invertible left_invertible for multLoopStr;
  coherence;
end;

registration
  cluster Trivial-multLoopStr -> invertible;
  coherence
  proof
    set M = Trivial-multLoopStr;
    thus M is right_invertible
    proof
      let x be Element of M;
      take x;
      thus thesis by STRUCT_0:def 10;
    end;
    let x being Element of M;
    take x;
    thus thesis by STRUCT_0:def 10;
  end;
end;

registration
  cluster invertible mult-cancelable strict 1-element for multLoopStr;
  existence
  proof
    take Trivial-multLoopStr;
    thus thesis;
  end;
end;

registration
  let M be left_invertible multLoopStr;
  cluster -> left_invertible for Element of M;
  coherence by Def31;
end;

registration
  let M be right_invertible multLoopStr;
  cluster -> right_invertible for Element of M;
  coherence by Def32;
end;

begin :: Almost

definition
  struct (multLoopStr,ZeroOneStr) multLoopStr_0 (# carrier -> set, multF ->
    BinOp of the carrier, ZeroF, OneF -> Element of the carrier #);
end;

registration
  let D,o,d,e;
  cluster multLoopStr_0(#D,o,d,e#) -> non empty;
  coherence;
end;

registration
  let T,f,s,t;
  cluster multLoopStr_0(#T,f,s,t#) -> trivial;
  coherence;
end;

registration
  let N,b,m,n;
  cluster multLoopStr_0(#N,b,m,n#) -> non trivial;
  coherence;
end;

definition
  func Trivial-multLoopStr_0 -> multLoopStr_0 equals
  multLoopStr_0(#{0}, op2,op0, op0 #);
  coherence;
end;

registration
  cluster Trivial-multLoopStr_0 -> 1-element strict;
  coherence;
end;

registration
  cluster strict 1-element for multLoopStr_0;
  existence
  proof
    take Trivial-multLoopStr_0;
    thus thesis;
  end;
end;

::$CD

definition
  let M be multLoopStr_0;
  attr M is almost_left_cancelable means
  for x being Element of M st x <> 0.M holds x is left_mult-cancelable;
  attr M is almost_right_cancelable means
  for x being Element of M st x <> 0.M holds x is right_mult-cancelable;
end;

definition
  let M be multLoopStr_0;
  attr M is almost_cancelable means
  M is almost_left_cancelable almost_right_cancelable;
end;

registration
  cluster almost_right_cancelable almost_left_cancelable -> almost_cancelable
    for multLoopStr_0;
  coherence;
  cluster almost_cancelable -> almost_right_cancelable almost_left_cancelable
    for multLoopStr_0;
  coherence;
end;

registration
  cluster Trivial-multLoopStr_0 -> almost_cancelable;
  coherence
  proof
    set M = Trivial-multLoopStr_0;
    thus M is almost_left_cancelable
    by STRUCT_0:def 10;
    let x be Element of M;
    assume x <> 0.M;
    let y,z being Element of M;
    assume y*x = z*x;
    thus thesis by STRUCT_0:def 10;
  end;
end;

registration
  cluster almost_cancelable strict 1-element for multLoopStr_0;
  existence
  proof
    take Trivial-multLoopStr_0;
    thus thesis;
  end;
end;

definition
  let M be multLoopStr_0;
  attr M is almost_left_invertible means
  for x being Element of M st x <> 0.M holds x is left_invertible;
  attr M is almost_right_invertible means
  for x being Element of M st x <> 0.M holds x is right_invertible;
end;

definition
  let M be multLoopStr_0;
  attr M is almost_invertible means
  M is almost_right_invertible almost_left_invertible;
end;

registration
  cluster almost_right_invertible almost_left_invertible -> almost_invertible
    for multLoopStr_0;
  coherence;
  cluster almost_invertible -> almost_right_invertible almost_left_invertible
    for multLoopStr_0;
  coherence;
end;

registration
  cluster Trivial-multLoopStr_0 -> almost_invertible;
  coherence
  proof
    set M = Trivial-multLoopStr_0;
    thus M is almost_right_invertible
    by STRUCT_0:def 10;
    let x being Element of M;
    assume x <> 0.M;
    take x;
    thus thesis by STRUCT_0:def 10;
  end;
end;

registration
  cluster almost_invertible almost_cancelable strict 1-element
    for multLoopStr_0;
  existence
  proof
    take Trivial-multLoopStr_0;
    thus thesis;
  end;
end;

begin :: Double

definition
  struct(addLoopStr,multLoopStr_0) doubleLoopStr (# carrier -> set, addF,
    multF -> BinOp of the carrier, OneF, ZeroF -> Element of the carrier #);
end;

registration
  let D,o,o1,d,e;
  cluster doubleLoopStr(#D,o,o1,d,e#) -> non empty;
  coherence;
end;

registration
  let T,f,f1,s,t;
  cluster doubleLoopStr(#T,f,f1,s,t#) -> trivial;
  coherence;
end;

registration
  let N,b,b1,m,n;
  cluster doubleLoopStr(#N,b,b1,m,n#) -> non trivial;
  coherence;
end;

definition
  func Trivial-doubleLoopStr -> doubleLoopStr equals
  doubleLoopStr(#{0}, op2, op2, op0, op0 #);
  coherence;
end;

registration
  cluster Trivial-doubleLoopStr -> 1-element strict;
  coherence;
end;

registration
  cluster strict 1-element for doubleLoopStr;
  existence
  proof
    take Trivial-doubleLoopStr;
    thus thesis;
  end;
end;

definition
 let M be multLoopStr, x,y be Element of M;
 func x/y -> Element of M equals x*/y;
 coherence;
end;