  
  [1X6 [33X[0;0YRight Modules over Path Algebras[133X[101X
  
  [33X[0;0YThere are two implementations of right modules over path algebras. The first
  type  are  matrix  modules  that  are  defined  by  vector spaces and linear
  transformations.   The  second  type  is  presentations  defined  by  vertex
  projective modules (see [14X6.7[114X).[133X
  
  
  [1X6.1 [33X[0;0YModules of matrix type[133X[101X
  
  [33X[0;0YThe first implementation of right modules over path algebras views them as a
  collection  of  vector spaces and linear transformations. Each vertex in the
  path  algebra  is  associated  with  a  vector  space  over the field of the
  algebra.  For each vertex [23Xv[123X of the algebra there is a vector space [23XV[123X. Arrows
  of the algebra are then associated with linear transformations which map the
  vector  space of the source vertex to the vector space of the target vertex.
  For  example,  if  [23Xa[123X is an arrow from [23Xv[123X to [23Xw[123X, then there is a transformation
  from  vector  space [23XV[123X to [23XW[123X. Given the dimension vector of the module we want
  to  construct,  the  information  we  need to provide is the non-zero linear
  transformations. The size of the matrices for the zero linear transformation
  are  given when we know the dimension vector. Alternatively, if we enter all
  the  transformations,  we  can  create  the  vector  spaces  of  the correct
  dimension,  and check to make sure the dimensions all agree. We can create a
  module in this way as follows.[133X
  
  [1X6.1-1 RightModuleOverPathAlgebra[101X
  
  [33X[1;0Y[29X[2XRightModuleOverPathAlgebra[102X( [3XA[103X, [3Xdim_vector[103X, [3Xgens[103X ) [32X operation[133X
  [33X[1;0Y[29X[2XRightModuleOverPathAlgebra[102X( [3XA[103X, [3Xmats[103X ) [32X operation[133X
  [33X[1;0Y[29X[2XRightModuleOverPathAlgebraNC[102X( [3XA[103X, [3Xmats[103X ) [32X operation[133X
  
  [33X[0;0YArguments:  [3XA[103X  --  a  (quotient  of  a)  path  algebra and [3Xdim_vector[103X -- the
  dimension  vector  of  the  module,  [3Xgens[103X or [3Xmats[103X -- a list of matrices. For
  further explanations, see below.[133X
  
  [6XReturns:[106X  [33X[0;10Ya module over a path algebra or over a qoutient of a path algebra.[133X
  
  [33X[0;0YIn  the first function call, the second argument [3Xdim_vector[103X is the dimension
  vector of the module, and the last argument [3Xgens[103X (maybe an empty list [10X[][110X) is
  a  list of elements of the form [10X["label",matrix][110X. This function constructs a
  right  module  over  a  (quotient of a) path algebra [3XA[103X with dimension vector
  [3Xdim_vector[103X,  and where the generators/arrows with a non-zero action is given
  in    the    list    [3Xgens[103X.    The    format    of    the    list   [3Xgens[103X   is
  [["a",[matrix_a]],["b",[matrix_b]],...],  where  "a"  and  "b" are labels of
  arrows  used  when  the  underlying  quiver  was created and matrix_? is the
  action of the algebra element corresponding to the arrow with label "?". The
  action of the arrows can be entered in any order. The function checks (i) if
  the algebra [3XA[103X is a (quotient of a) path algebra, (ii) if the matrices of the
  action of the arrows have the correct size according to the dimension vector
  entered,  (iii)  also  whether  or  not  the  relations  of  the algebra are
  satisfied and (iv) if all matrices are over the correct field.[133X
  
  [33X[0;0YIn  the  second  function  call, the list of matrices [3Xmats[103X can take on three
  different forms. The function checks (i), (ii), (iii) and (iv) as above.[133X
  
  [33X[0;0Y1) The argument [3Xmats[103X can be a list of blocks of matrices where each block is
  of  the  form,  `["name of arrow",matrix]'. So if you named your arrows when
  you  created  the  quiver,  then  you can associate a matrix with that arrow
  explicitly.[133X
  
  [33X[0;0Y2)  The  argument  [3Xmats[103X is just a list of matrices, and the matrices will be
  associated  to  the  arrows in the order of arrow creation. If when creating
  the  quiver,  the arrow [23Xa[123X was created first, then [23Xa[123X would be associated with
  the first matrix.[133X
  
  [33X[0;0Y3)  The  method  is  very much the same as the second method. If [3Xarrows[103X is a
  list  of  the  arrows of the quiver (obtained for instance through [10Xarrows :=
  ArrowsOfQuiver(Q);[110X),    the    argument    [3Xmats[103X    can   have   the   format
  [10X[[arrows[1],matrix_1],[arrows[2],matrix_2],.... ].[110X[133X
  
  [33X[0;0YIf  you  would  like  the  trivial vector space at any vertex, then for each
  incoming arrow "a", associate it with a list of the form [10X["a",[n,0]][110X where n
  is  the  dimension  of  the  vector space at the source vertex of the arrow.
  Likewise  for  all  outgoing  arrows  "b", associate them to a block of form
  [10X["b",[0,n]][110X  where  n  is  the  dimension  of the vector space at the target
  vertex of the arrow.[133X
  
  [33X[0;0YThe third function call is the same as the second except that the check (iv)
  is not performed.[133X
  
  [33X[0;0YA  warning  though,  the  function assumes that you do not mix the styles of
  inputting  the  matrices/linear  transformations associated to the arrows in
  the  quiver.  Furthermore  in  the two last versions, each arrow needs to be
  assigned a matrix, otherwise an error will be returned.[133X
  
  [1X6.1-2 RightAlgebraModuleToPathAlgebraMatModule[101X
  
  [33X[1;0Y[29X[2XRightAlgebraModuleToPathAlgebraMatModule[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a right module over an algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ya module over a (qoutient of a) path algebra.[133X
  
  [33X[0;0YThis  function constructs a right module over a (quotient of a) path algebra
  [22XA[122X  from a RightAlgebraModule over the same algebra [22XA[122X. The function checks if
  [22XA[122X  actually  is  a  quotient of a path algebra and if the module [22XM[122X is finite
  dimensional and if not, it returns an error message.[133X
  
  [1X6.1-3 \=[101X
  
  [33X[1;0Y[29X[2X\=[102X( [3XM[103X, [3XN[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM, N[103X -- two path algebra matrix modules.[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue  if  [3XM[103X  and  [3XN[103X  has  the  same dimension vectors and the same
            matrices defining the module structure.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XQ := Quiver(2, [[1, 2, "a"], [2, 1, "b"],[1, 1, "c"]]);[127X[104X
    [4X[28X<quiver with 2 vertices and 3 arrows>[128X[104X
    [4X[25Xgap>[125X [27XP := PathAlgebra(Rationals, Q);[127X[104X
    [4X[28X<Rationals[<quiver with 2 vertices and 3 arrows>]>[128X[104X
    [4X[25Xgap>[125X [27Xmatrices := [["a", [[1,0,0],[0,1,0]]], [127X[104X
    [4X[25X>[125X [27X ["b", [[0,1],[1,0],[0,1]]],[127X[104X
    [4X[25X>[125X [27X ["c", [[0,0],[1,0]]]];[127X[104X
    [4X[28X[ [ "a", [ [ 1, 0, 0 ], [ 0, 1, 0 ] ] ], [128X[104X
    [4X[28X  [ "b", [ [ 0, 1 ], [ 1, 0 ], [ 0, 1 ] ] ], [128X[104X
    [4X[28X  [ "c", [ [ 0, 0 ], [ 1, 0 ] ] ] ][128X[104X
    [4X[25Xgap>[125X [27XM := RightModuleOverPathAlgebra(P,matrices);[127X[104X
    [4X[28X<[ 2, 3 ]>[128X[104X
    [4X[25Xgap>[125X [27Xmats := [ [[1,0,0], [0,1,0]], [[0,1],[1,0],[0,1]], [127X[104X
    [4X[25X>[125X [27X          [[0,0],[1,0]] ];; [127X[104X
    [4X[25Xgap>[125X [27XN := RightModuleOverPathAlgebra(P,mats); [127X[104X
    [4X[28X<[ 2, 3 ]>[128X[104X
    [4X[25Xgap>[125X [27Xarrows := ArrowsOfQuiver(Q);[127X[104X
    [4X[28X[ a, b, c ][128X[104X
    [4X[25Xgap>[125X [27Xmats := [[arrows[1], [[1,0,0],[0,1,0]]],[127X[104X
    [4X[25X>[125X [27X         [arrows[2], [[0,1],[1,0],[0,1]]], [127X[104X
    [4X[25X>[125X [27X         [arrows[3], [[0,0],[1,0]]]];;[127X[104X
    [4X[25Xgap>[125X [27XN := RightModuleOverPathAlgebra(P,mats); [127X[104X
    [4X[28X<[ 2, 3 ]>[128X[104X
    [4X[25Xgap>[125X [27X# Next we give the vertex simple associate to vertex 1. [127X[104X
    [4X[25Xgap>[125X [27XM := RightModuleOverPathAlgebra(P,[["a",[1,0]],["b",[0,1]],[127X[104X
    [4X[25X>[125X [27X             ["c",[[0]]]]);[127X[104X
    [4X[28X<[ 1, 0 ]>[128X[104X
    [4X[25Xgap>[125X [27X# The zero module. [127X[104X
    [4X[25Xgap>[125X [27XM := RightModuleOverPathAlgebra(P,[["a",[0,0]],["b",[0,0]],[127X[104X
    [4X[25X>[125X [27X             ["c",[0,0]]]);[127X[104X
    [4X[28X<[ 0, 0 ]>[128X[104X
    [4X[25Xgap>[125X [27XDimension(M);[127X[104X
    [4X[28X0[128X[104X
    [4X[25Xgap>[125X [27XBasis(M);[127X[104X
    [4X[28XBasis( <[ 0, 0 ]>, ... )[128X[104X
    [4X[25Xgap>[125X [27Xmatrices := [["a", [[1,0,0],[0,1,0]]], ["b",[127X[104X
    [4X[25X>[125X [27X [[0,1],[1,0],[0,1]]], ["c", [[0,0],[1,0]]]];[127X[104X
    [4X[28X[ [ "a", [ [ 1, 0, 0 ], [ 0, 1, 0 ] ] ], [128X[104X
    [4X[28X  [ "b", [ [ 0, 1 ], [ 1, 0 ], [ 0, 1 ] ] ], [128X[104X
    [4X[28X  [ "c", [ [ 0, 0 ], [ 1, 0 ] ] ] ][128X[104X
    [4X[25Xgap>[125X [27XM := RightModuleOverPathAlgebra(P,[2,3],matrices);[127X[104X
    [4X[28X<[ 2, 3 ]>[128X[104X
    [4X[25Xgap>[125X [27XM := RightModuleOverPathAlgebra(P,[2,3],[]);  [127X[104X
    [4X[28X<[ 2, 3 ]>[128X[104X
    [4X[25Xgap>[125X [27XA := P/[P.c^2 - P.a*P.b, P.a*P.b*P.c, P.b*P.c];         [127X[104X
    [4X[28X<Rationals[<quiver with 2 vertices and 3 arrows>]/[128X[104X
    [4X[28X<two-sided ideal in <Rationals[<quiver with 2 vertices and 3 arrows>]>[128X[104X
    [4X[28X    , (4 generators)>>[128X[104X
    [4X[25Xgap>[125X [27XDimension(A);[127X[104X
    [4X[28X9[128X[104X
    [4X[25Xgap>[125X [27XAmod := RightAlgebraModule(A,\*,A);                       [127X[104X
    [4X[28X<9-dimensional right-module over <Rationals[<quiver with [128X[104X
    [4X[28X2 vertices and 3 arrows>]/[128X[104X
    [4X[28X<two-sided ideal in <Rationals[<quiver with 2 vertices and 3 arrows>]>[128X[104X
    [4X[28X    , (4 generators)>>>[128X[104X
    [4X[25Xgap>[125X [27XRightAlgebraModuleToPathAlgebraMatModule(Amod);[127X[104X
    [4X[28X<[ 4, 5 ]> [128X[104X
  [4X[32X[104X
  
  
  [1X6.2 [33X[0;0YCategories Of Matrix Modules[133X[101X
  
  [1X6.2-1 IsPathAlgebraMatModule[101X
  
  [33X[1;0Y[29X[2XIsPathAlgebraMatModule[102X( [3Xobject[103X ) [32X filter[133X
  [6XReturns:[106X  [33X[0;10Ytrue  or false depending on whether [3Xobject[103X belongs to the category
            [10XIsPathAlgebraMatModule[110X.[133X
  
  [33X[0;0YThese  matrix  modules  fall  under  the category `IsAlgebraModule' with the
  added  filter  of `IsPathAlgebraMatModule'. Operations available for algebra
  modules   can   be   applied   to   path  algebra  modules.  See  [14XReference:
  Representations  of Algebras[114X for more details. These modules are also vector
  spaces  over  the  field  of the path algebra. So refer to [14XReference: Vector
  Spaces[114X for descriptions of the basis and elementwise operations available.[133X
  
  
  [1X6.3 [33X[0;0YActing on Module Elements[133X[101X
  
  [1X6.3-1 ^[101X
  
  [33X[1;0Y[29X[2X^[102X( [3Xm[103X, [3Xp[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xm[103X -- an element in a module, [3Xp[103X -- an element in a quiver algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe element [3Xm[103X multiplied with [3Xp[103X.[133X
  
  [33X[0;0YWhen you act on an module element [23Xm[123X by an arrow [23Xa[123X from [23Xv[123X to [23Xw[123X, the component
  of  [23Xm[123X  from [23XV[123X is acted on by [23XL[123X the transformation associated to [23Xa[123X and placed
  in the component [23XW[123X. All other components are given the value [23X0[123X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27X# Using the path algebra P from the above example. [127X[104X
    [4X[25Xgap>[125X [27Xmatrices := [["a", [[1,0,0],[0,1,0]]], [127X[104X
    [4X[25X>[125X [27X["b", [[0,1],[1,0],[0,1]]], ["c", [[0,0],[1,0]]]];[127X[104X
    [4X[28X[ [ "a", [ [ 1, 0, 0 ], [ 0, 1, 0 ] ] ], [128X[104X
    [4X[28X  [ "b", [ [ 0, 1 ], [ 1, 0 ], [ 0, 1 ] ] ], [128X[104X
    [4X[28X  [ "c", [ [ 0, 0 ], [ 1, 0 ] ] ] ][128X[104X
    [4X[25Xgap>[125X [27XM := RightModuleOverPathAlgebra(P,matrices);[127X[104X
    [4X[28X<[ 2, 3 ]>[128X[104X
    [4X[25Xgap>[125X [27XB:=BasisVectors(Basis(M));[127X[104X
    [4X[28X[ [ [ 1, 0 ], [ 0, 0, 0 ] ], [ [ 0, 1 ], [ 0, 0, 0 ] ], [128X[104X
    [4X[28X  [ [ 0, 0 ], [ 1, 0, 0 ] ], [ [ 0, 0 ], [ 0, 1, 0 ] ], [128X[104X
    [4X[28X  [ [ 0, 0 ], [ 0, 0, 1 ] ] ][128X[104X
    [4X[25Xgap>[125X [27XB[1] + B[3];[127X[104X
    [4X[28X[ [ 1, 0 ], [ 1, 0, 0 ] ][128X[104X
    [4X[25Xgap>[125X [27X4*B[2];[127X[104X
    [4X[28X[ [ 0, 4 ], [ 0, 0, 0 ] ][128X[104X
    [4X[25Xgap>[125X [27Xm := 5*B[1] + 2*B[4]+B[5];[127X[104X
    [4X[28X[ [ 5, 0 ], [ 0, 2, 1 ] ][128X[104X
    [4X[25Xgap>[125X [27Xm^(P.a*P.b-P.c);[127X[104X
    [4X[28X[ [ 0, 5 ], [ 0, 0, 0 ] ][128X[104X
    [4X[25Xgap>[125X [27XB[1]^P.a;[127X[104X
    [4X[28X[ [ 0, 0 ], [ 1, 0, 0 ] ][128X[104X
    [4X[25Xgap>[125X [27XB[2]^P.b;[127X[104X
    [4X[28X[ [ 0, 0 ], [ 0, 0, 0 ] ][128X[104X
    [4X[25Xgap>[125X [27XB[4]^(P.b*P.c);[127X[104X
    [4X[28X[ [ 0, 0 ], [ 0, 0, 0 ] ] [128X[104X
  [4X[32X[104X
  
  
  [1X6.4 [33X[0;0YOperations on representations[133X[101X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XQ  := Quiver(3,[[1,2,"a"],[1,2,"b"],[2,2,"c"],[2,3,"d"],[127X[104X
    [4X[25X>[125X [27X[3,1,"e"]]);[127X[104X
    [4X[28X<quiver with 3 vertices and 5 arrows>[128X[104X
    [4X[25Xgap>[125X [27XKQ := PathAlgebra(Rationals, Q);[127X[104X
    [4X[28X<Rationals[<quiver with 3 vertices and 5 arrows>]>[128X[104X
    [4X[25Xgap>[125X [27Xgens := GeneratorsOfAlgebra(KQ);[127X[104X
    [4X[28X[ (1)*v1, (1)*v2, (1)*v3, (1)*a, (1)*b, (1)*c, (1)*d, (1)*e ][128X[104X
    [4X[25Xgap>[125X [27Xu := gens[1];; v := gens[2];;[127X[104X
    [4X[25Xgap>[125X [27Xw := gens[3];; a := gens[4];;[127X[104X
    [4X[25Xgap>[125X [27Xb := gens[5];; c := gens[6];;[127X[104X
    [4X[25Xgap>[125X [27Xd := gens[7];; e := gens[8];;[127X[104X
    [4X[25Xgap>[125X [27Xrels := [d*e,c^2,a*c*d-b*d,e*a];;[127X[104X
    [4X[25Xgap>[125X [27XA := KQ/rels;[127X[104X
    [4X[28X<Rationals[<quiver with 3 vertices and 5 arrows>]/[128X[104X
    [4X[28X<two-sided ideal in <Rationals[<quiver with 3 vertices and 5 arrows>]>[128X[104X
    [4X[28X    , (5 generators)>>[128X[104X
    [4X[25Xgap>[125X [27Xmat := [["a",[[1,2],[0,3],[1,5]]],["b",[[2,0],[3,0],[5,0]]],[127X[104X
    [4X[25X>[125X [27X["c",[[0,0],[1,0]]],["d",[[1,2],[0,1]]],["e",[[0,0,0],[0,0,0]]]];;[127X[104X
    [4X[25Xgap>[125X [27XN := RightModuleOverPathAlgebra(A,mat);   [127X[104X
    [4X[28X<[ 3, 2, 2 ]> [128X[104X
  [4X[32X[104X
  
  [1X6.4-1 AnnihilatorOfModule[101X
  
  [33X[1;0Y[29X[2XAnnihilatorOfModule[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  basis  of  the  annihilator  of  the  module  [3XM[103X  in  the finite
            dimensional algebra over which [3XM[103X is a module.[133X
  
  [1X6.4-2 BasicVersionOfModule[101X
  
  [33X[1;0Y[29X[2XBasicVersionOfModule[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  basic  version  of  the  entered module [3XM[103X, that is, if [23XM \simeq
            M_1^{n_1}   \oplus   \cdots   \oplus   M_t^{n_t},[123X   where  [23XM_i[123X  is
            indecomposable,  then  [23XM_1\oplus \cdots \oplus M_t[123X is returned. At
            present,  this  function  only work at best for finite dimensional
            (quotients  of  a) path algebra over a finite field. If [3XM[103X is zero,
            then [3XM[103X is returned.[133X
  
  [1X6.4-3 BlockDecompositionOfModule[101X
  
  [33X[1;0Y[29X[2XBlockDecompositionOfModule[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  set  of  modules  [23X\{M_1,..., M_t\}[123X such that [23XM \simeq M_1\oplus
            \cdots  \oplus  M_t,[123X where each [23XM_i[123X is isomorphic to [23XX_i^{n_i}[123X for
            some indecomposable module [23XX_i[123X and positive integer [23Xn_i[123X for all [23Xi[123X,
            where [22XX_i≄ X_j[122X for [22Xi≠ j[122X.[133X
  
  [1X6.4-4 BlockSplittingIdempotents[101X
  
  [33X[1;0Y[29X[2XBlockSplittingIdempotents[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  set  [23X\{e_1,...,  e_t\}[123X  of idempotents in the endomorphism of [3XM[103X
            such that [23XM \simeq \Im e_1\oplus \cdots \oplus \Im e_t,[123X where each
            [23X\Im  e_i[123X  is  isomorphic  to  [23XX_i^{n_i}[123X  for  some  module [23XX_i[123X and
            positive integer [23Xn_i[123X for all [23Xi[123X.[133X
  
  [1X6.4-5 CommonDirectSummand[101X
  
  [33X[1;0Y[29X[2XCommonDirectSummand[102X( [3XM[103X, [3XN[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X and [3XN[103X -- two path algebra modules.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  list of four modules [[3XX[103X,[3XU[103X,[3XX[103X, [3XV[103X], where [3XX[103X is one common non-zero
            direct  summand of [3XM[103X and [3XN[103X, the sum of [3XX[103X and [3XU[103X is [3XM[103X and the sum of
            [3XX[103X  and [3XV[103X is [3XN[103X, if such a non-zero direct summand exists. Otherwise
            it returns false.[133X
  
  [33X[0;0YThe  function  checks  if  [3XM[103X  and  [3XN[103X are [10XPathAlgebraMatModule[110Xs over the same
  (quotient of a) path algebra.[133X
  
  [1X6.4-6 ComplexityOfModule[101X
  
  [33X[1;0Y[29X[2XComplexityOfModule[102X( [3XM[103X, [3Xn[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- path algebdra module, [3Xn[103X -- a positive integer.[133X
  
  [6XReturns:[106X  [33X[0;10Yan estimate of the complexity of the module [3XM[103X.[133X
  
  [33X[0;0YThe function checks if the algebra over which the module [3XM[103X lives is known to
  have  finite  global dimension. If so, it returns complexity zero. Otherwise
  it  tries  to estimate the complexity in the following way. Recall that if a
  function  [22Xf(x)[122X is a polynomial in [22Xx[122X, the degree of [22Xf(x)[122X is given by [22Xlim_n->∞
  fraclog  |f(n)|log  n[122X.  So  then  this  function computes an estimate of the
  complexity  of  [3XM[103X  by  approximating the complexity by considering the limit
  [22Xlim_m->  ∞ log fracdim(P(M)(m))log m[122X where [22XP(M)(m)[122X is the [22Xm[122X-th projective in
  a  minimal projective resolution of [3XM[103X at stage [22Xm[122X. This limit is estimated by
  [22Xfraclog dim(P(M)(n))log n[122X.[133X
  
  [1X6.4-7 DecomposeModule[101X
  
  [33X[1;0Y[29X[2XDecomposeModule[102X( [3XM[103X ) [32X operation[133X
  [33X[1;0Y[29X[2XDecomposeModuleWithInclusions[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ya list of indecomposable modules whose direct sum is isomorphic to
            the  module  [3XM[103X in first variant. The second variant returns a list
            of  inclusions  into [3XM[103X with the sum of the images is isomorphic to
            the module [3XM[103X.[133X
  
  [33X[0;0YWarning:  the  function  is  not  properly  tested and it at best only works
  properly over finite fields.[133X
  
  [1X6.4-8 DecomposeModuleProbabilistic[101X
  
  [33X[1;0Y[29X[2XDecomposeModuleProbabilistic[102X( [3XHomMM[103X, [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments:  [3XHomMM[103X,  [3XM[103X  --  a  list of basis elements of the Hom-space of the
  entered module and a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ywith (hopefully high probability) a list of indecomposable modules
            whose direct sum is isomorphic to the module [3XM[103X.[133X
  
  [33X[0;0YGiven a module [3XM[103X over a finite dimensional quotient of a path algebra over a
  finite  field,  this  function  tries  to  decompose the entered module [3XM[103X by
  choosing   random   elements  in  the  endomorphism  ring  of  [3XM[103X  which  are
  non-nilpotent  and  non-invertible.  Such  elements splits the module in two
  direct  summands,  and  the  procedure  does  this  as long as it finds such
  elements.  The  output  is  not  guaranteed  to  be a list of indecomposable
  modules,  but  their  direct sum is isomorphic to the entered module [3XM[103X. This
  was  constructed  as  joint  effort  by  the  participants  at  the workshop
  "Persistence,  Representations, and Computation", February 26th - March 2nd,
  2018". This is an experimental function, so use with caution.[133X
  
  [1X6.4-9 DecomposeModuleViaCharPoly[101X
  
  [33X[1;0Y[29X[2XDecomposeModuleViaCharPoly[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  list  with  high  probability  of  indecomposable modules whose
            direct sum is isomorphic to the module [3XM[103X.[133X
  
  [33X[0;0YGiven a module [3XM[103X over a finite dimensional quotient of a path algebra over a
  finite field, this function decomposes the entered module [3XM[103X by computing the
  endomorphism  ring  of  [3XM[103X  and  choosing  random  elements in it. This is an
  experimental function, so use with caution.[133X
  
  [1X6.4-10 DecomposeModuleViaTop[101X
  
  [33X[1;0Y[29X[2XDecomposeModuleViaTop[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ya list of indecomposable modules whose direct sum is isomorphic to
            the module [3XM[103X.[133X
  
  [33X[0;0YGiven a module [3XM[103X over a finite dimensional quotient of a path algebra over a
  finite  field,  this function decomposes the entered module [3XM[103X by finding the
  image [22XΣ[122X of the endomorphism ring of [3XM[103X in the endomorphism ring of the top of
  [3XM[103X,  in  [22XΣ[122X  finds a complete set of primitive idempotents, lifts them back to
  the  endomorphism  ring  of  [3XM[103X  and  decomposes  [3XM[103X.  This is an experimental
  function, so use with caution.[133X
  
  [1X6.4-11 DecomposeModuleWithMultiplicities[101X
  
  [33X[1;0Y[29X[2XDecomposeModuleWithMultiplicities[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  list  of  length  two,  where  the first entry is a list of all
            indecomposable  non-isomorphic direct summands of [3XM[103X and the second
            entry is the list of the multiplicities of these direct summand in
            the module [3XM[103X.[133X
  
  [33X[0;0YWarning:  the  function  is  not  properly  tested and it at best only works
  properly over finite fields.[133X
  
  [1X6.4-12 Dimension[101X
  
  [33X[1;0Y[29X[2XDimension[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe dimension of the representation [3XM[103X.[133X
  
  [1X6.4-13 DimensionVector[101X
  
  [33X[1;0Y[29X[2XDimensionVector[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe dimension vector of the representation [3XM[103X.[133X
  
  [1X6.4-14 DirectSumOfQPAModules[101X
  
  [33X[1;0Y[29X[2XDirectSumOfQPAModules[102X( [3XL[103X ) [32X operation[133X
  
  [33X[0;0YArguments:  [3XL[103X  -- a list of [10XPathAlgebraMatModule[110Xs over the same (quotient of
  a) path algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe direct sum of the representations contained in the list [3XL[103X.[133X
  
  [33X[0;0YIn    addition    three    attributes    are   attached   to   the   result,
  [2XIsDirectSumOfModules[102X       ([14X6.4-20[114X),      [2XDirectSumProjections[102X      ([14X6.4-16[114X)
  [2XDirectSumInclusions[102X ([14X6.4-15[114X).[133X
  
  [1X6.4-15 DirectSumInclusions[101X
  
  [33X[1;0Y[29X[2XDirectSumInclusions[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe list of inclusions from the individual modules to their direct
            sum,    when   a   direct   sum   has   been   constructed   using
            [2XDirectSumOfQPAModules[102X ([14X6.4-14[114X).[133X
  
  [1X6.4-16 DirectSumProjections[101X
  
  [33X[1;0Y[29X[2XDirectSumProjections[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  list  of  projections  from  the direct sum to the individual
            modules  used  to construct direct sum, when a direct sum has been
            constructed using [2XDirectSumOfQPAModules[102X ([14X6.4-14[114X).[133X
  
  [1X6.4-17 FromIdentityToDoubleStarHomomorphism[101X
  
  [33X[1;0Y[29X[2XFromIdentityToDoubleStarHomomorphism[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe homomorphism from [3XM[103X to the double star of the module [3XM[103X.[133X
  
  [1X6.4-18 IntersectionOfSubmodules[101X
  
  [33X[1;0Y[29X[2XIntersectionOfSubmodules[102X( [3Xlist[103X ) [32X operation[133X
  
  [33X[0;0YArguments:  [3Xf,  g[103X or [3Xlist[103X -- two homomorphisms of PathAlgebraMatModules or a
  list of such.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  subrepresentation  given  by  the  intersection  of  all  the
            submodules given by the inclusions [3Xf[103X and [3Xg[103X or [3Xlist[103X.[133X
  
  [33X[0;0YThe  function  checks if [3Xlist[103X is non-empty and if [23X[3Xf[103X\colon M\to X[123X and [23X[3Xg[103X\colon
  N\to  X[123X  or all the homomorphism in [3Xlist[103X have the same range and if they all
  are  inclusions.  If  the  function  is given two arguments [3Xf[103X and [3Xg[103X, then it
  returns  [23X[f',g',g'*f][123X,  where [23Xf'\colon E\to N[123X, [23Xg'\colon E\to M[123X, and [23XE[123X is the
  pullback of [3Xf[103X and [3Xg[103X. For a list of inclusions it returns a monomorphism from
  a module isomorphic to the intersection to [23XX[123X.[133X
  
  [1X6.4-19 IsDirectSummand[101X
  
  [33X[1;0Y[29X[2XIsDirectSummand[102X( [3XM[103X, [3XN[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM, N[103X -- two path algebra modules ([10XPathAlgebraMatModule[110Xs).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if [3XM[103X is isomorphic to a direct summand of [3XN[103X, otherwise false.[133X
  
  [33X[0;0YThe  function  checks  if  [3XM[103X  and  [3XN[103X are [10XPathAlgebraMatModule[110Xs over the same
  (quotient of a) path algebra.[133X
  
  [1X6.4-20 IsDirectSumOfModules[101X
  
  [33X[1;0Y[29X[2XIsDirectSumOfModules[102X( [3XM[103X ) [32X filter[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue  if  [3XM[103X  is  constructed via the command [2XDirectSumOfQPAModules[102X
            ([14X6.4-14[114X).[133X
  
  [33X[0;0YUsing the example above.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XN2 := DirectSumOfQPAModules([N,N]);[127X[104X
    [4X[28X<[ 6, 4, 4 ]>[128X[104X
    [4X[25Xgap>[125X [27Xproj := DirectSumProjections(N2);[127X[104X
    [4X[28X[ <<[ 6, 4, 4 ]> ---> <[ 3, 2, 2 ]>>[128X[104X
    [4X[28X    , <<[ 6, 4, 4 ]> ---> <[ 3, 2, 2 ]>>[128X[104X
    [4X[28X     ][128X[104X
    [4X[25Xgap>[125X [27Xinc := DirectSumInclusions(N2);[127X[104X
    [4X[28X[ <<[ 3, 2, 2 ]> ---> <[ 6, 4, 4 ]>>[128X[104X
    [4X[28X    , <<[ 3, 2, 2 ]> ---> <[ 6, 4, 4 ]>>[128X[104X
    [4X[28X     ] [128X[104X
  [4X[32X[104X
  
  [1X6.4-21 IsExceptionalModule[101X
  
  [33X[1;0Y[29X[2XIsExceptionalModule[102X( [3XM[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if [3XM[103X is an exceptional module, otherwise false, if the field,
            over which the algebra [3XM[103X is defined over, is finite.[133X
  
  [33X[0;0YThe  module  [3XM[103X  is  an  exceptional  module,  if  it  is  indecomposable and
  [22XExt^1(M,M)=(0)[122X.[133X
  
  [1X6.4-22 IsIndecomposableModule[101X
  
  [33X[1;0Y[29X[2XIsIndecomposableModule[102X( [3XM[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue  if  [3XM[103X  is an indecomposable module, if the field, over which
            the algebra [3XM[103X is defined over, is finite. If [3XM[103X is the zero module,
            then [10Xfalse[110X is returned.[133X
  
  [1X6.4-23 IsInAdditiveClosure[101X
  
  [33X[1;0Y[29X[2XIsInAdditiveClosure[102X( [3XM[103X, [3XN[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM, N[103X -- two path algebra modules ([10XPathAlgebraMatModule[110Xs).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue  if  [3XM[103X  is in the additive closure of the module [3XN[103X, otherwise
            false.[133X
  
  [33X[0;0YThe  function  checks  if  [3XM[103X  and  [3XN[103X are [10XPathAlgebraMatModule[110Xs over the same
  (quotient of a) path algebra.[133X
  
  [1X6.4-24 IsInjectiveModule[101X
  
  [33X[1;0Y[29X[2XIsInjectiveModule[102X( [3XM[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if the representation [3XM[103X is injective.[133X
  
  [1X6.4-25 IsomorphicModules[101X
  
  [33X[1;0Y[29X[2XIsomorphicModules[102X( [3XM[103X, [3XN[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM, N[103X -- two path algebra modules ([10XPathAlgebraMatModule[110Xs).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue or false depending on whether [3XM[103X and [3XN[103X are isomorphic or not.[133X
  
  [33X[0;0YThe  function  first checks if the modules [3XM[103X and [3XN[103X are modules over the same
  algebra,  and  returns fail if not. The function returns true if the modules
  are isomorphic, otherwise false.[133X
  
  [1X6.4-26 IsProjectiveModule[101X
  
  [33X[1;0Y[29X[2XIsProjectiveModule[102X( [3XM[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if the representation [3XM[103X is projective.[133X
  
  [1X6.4-27 IsRigidModule[101X
  
  [33X[1;0Y[29X[2XIsRigidModule[102X( [3XM[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if [3XM[103X is a rigid module, otherwise false.[133X
  
  [33X[0;0YThe module [3XM[103X is a rigid module, if [22XExt^1(M,M)=(0)[122X.[133X
  
  [1X6.4-28 IsSemisimpleModule[101X
  
  [33X[1;0Y[29X[2XIsSemisimpleModule[102X( [3XM[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if the representation [3XM[103X is semisimple.[133X
  
  [1X6.4-29 IsSimpleQPAModule[101X
  
  [33X[1;0Y[29X[2XIsSimpleQPAModule[102X( [3XM[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if the representation [3XM[103X is simple.[133X
  
  [1X6.4-30 IsTauRigidModule[101X
  
  [33X[1;0Y[29X[2XIsTauRigidModule[102X( [3XM[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if [3XM[103X is a [22Xτ[122X-rigid module, otherwise false.[133X
  
  [33X[0;0YThe module [3XM[103X is a [22Xτ[122X-rigid module, if [22XHom(M,τ M)=(0)[122X.[133X
  
  [1X6.4-31 LoewyLength[101X
  
  [33X[1;0Y[29X[2XLoewyLength[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe Loewy length of the module [3XM[103X.[133X
  
  [33X[0;0YThe  function checks that the module [3XM[103X is a module over a finite dimensional
  quotient  of  a  path  algebra,  and  returns  fail  otherwise  (This is not
  implemented yet).[133X
  
  [1X6.4-32 IsZero[101X
  
  [33X[1;0Y[29X[2XIsZero[102X( [3XM[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if [3XM[103X is the zero module, otherwise false.[133X
  
  [1X6.4-33 MatricesOfPathAlgebraModule[101X
  
  [33X[1;0Y[29X[2XMatricesOfPathAlgebraModule[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ya  list  of  the  matrices  that defines the representation [3XM[103X as a
            right module of the acting path algebra.[133X
  
  [33X[0;0YThe  list  of  matrices  that are returned are not the same identical to the
  matrices  entered to define the representation if there is zero vector space
  in  at  least  one  vertex.  Then  zero matrices of the appropriate size are
  returned.[133X
  
  [1X6.4-34 MaximalCommonDirectSummand[101X
  
  [33X[1;0Y[29X[2XMaximalCommonDirectSummand[102X( [3XM[103X, [3XN[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM, N[103X -- two path algebra modules ([10XPathAlgebraMatModule[110Xs).[133X
  
  [6XReturns:[106X  [33X[0;10Ya  list  of  three  modules  [[3XX[103X,[3XU[103X,[3XV[103X],  where [3XX[103X is a maximal common
            non-zero  direct  summand  of [3XM[103X and [3XN[103X, the sum of [3XX[103X and [3XU[103X is [3XM[103X and
            the sum of [3XX[103X and [3XV[103X is [3XN[103X, if such a non-zero maximal direct summand
            exists. Otherwise it returns false.[133X
  
  [33X[0;0YThe  function  checks  if  [3XM[103X  and  [3XN[103X are [10XPathAlgebraMatModule[110Xs over the same
  (quotient of a) path algebra.[133X
  
  [1X6.4-35 NumberOfNonIsoDirSummands[101X
  
  [33X[1;0Y[29X[2XNumberOfNonIsoDirSummands[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra modules ([10XPathAlgebraMatModule[110Xs).[133X
  
  [6XReturns:[106X  [33X[0;10Ya  list  with  two  elements:  (1)  the  number  of non-isomorphic
            indecomposable  direct  summands  of  the  module  [3XM[103X  and  (2) the
            dimensions   of   the   simple   blocks  of  the  semisimple  ring
            [23X\End(M)/\rad \End(M)[123X.[133X
  
  [1X6.4-36 MinimalGeneratingSetOfModule[101X
  
  [33X[1;0Y[29X[2XMinimalGeneratingSetOfModule[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ya  minimal  generator  set of the module [3XM[103X as a module of the path
            algebra it is defined over.[133X
  
  [1X6.4-37 RadicalOfModule[101X
  
  [33X[1;0Y[29X[2XRadicalOfModule[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe radical of the module [3XM[103X.[133X
  
  [33X[0;0YThis  returns  only the representation given by the radical of the module [3XM[103X.
  The  operation  [2XRadicalOfModuleInclusion[102X  ([14X7.3-24[114X) computes the inclusion of
  the radical of [3XM[103X into [3XM[103X. This function applies when the algebra over which [3XM[103X
  is defined is an admissible quotient of a path algebra.[133X
  
  [1X6.4-38 RadicalSeries[101X
  
  [33X[1;0Y[29X[2XRadicalSeries[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe radical series of the module [3XM[103X.[133X
  
  [33X[0;0YThe  function  gives  the radical series as a list of vectors [10X[n_1,...,n_s][110X,
  where  the  algebra  has  [23Xs[123X  isomorphism  classes  of simple modules and the
  numbers  give  the  multiplicity  of  each  simple.  The first vector listed
  corresponds to the top layer, and so on.[133X
  
  [1X6.4-39 SocleSeries[101X
  
  [33X[1;0Y[29X[2XSocleSeries[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe socle series of the module [3XM[103X.[133X
  
  [33X[0;0YThe  function  gives  the  socle  series as a list of vectors [10X[n_1,...,n_s][110X,
  where  the  algebra  has  [23Xs[123X  isomorphism  classes  of simple modules and the
  numbers  give  the  multiplicity  of  each  simple.  The  last vector listed
  corresponds to the socle layer, and so on backwards.[133X
  
  [1X6.4-40 SocleOfModule[101X
  
  [33X[1;0Y[29X[2XSocleOfModule[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module ([10XPathAlgebraMatModule[110X).[133X
  
  [6XReturns:[106X  [33X[0;10Ythe socle of the module [3XM[103X.[133X
  
  [33X[0;0YThis  operation  only  return  the  representation given by the socle of the
  module  [3XM[103X.  The  inclusion  the  socle  of  [3XM[103X  into  [3XM[103X can be computed using
  [2XSocleOfModuleInclusion[102X ([14X7.3-26[114X).[133X
  
  [1X6.4-41 SubRepresentation[101X
  
  [33X[1;0Y[29X[2XSubRepresentation[102X( [3XM[103X, [3Xgens[103X ) [32X operation[133X
  
  [33X[0;0YArguments:  [3XM[103X  --  a  path  algebra  module  ([10XPathAlgebraMatModule[110X), [3Xgens[103X --
  elements in [3XM[103X.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe submodule of the module [3XM[103X generated by the elements [3Xgens[103X.[133X
  
  [33X[0;0YThe  function checks if [3Xgens[103X are elements in [3XM[103X, and returns an error message
  otherwise.  The  inclusion  of  the submodule generated by the elements [3Xgens[103X
  into [3XM[103X can be computed using [2XSubRepresentationInclusion[102X ([14X7.3-27[114X).[133X
  
  [1X6.4-42 SumOfSubmodules[101X
  
  [33X[1;0Y[29X[2XSumOfSubmodules[102X( [3Xlist[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xf, g[103X or [3Xlist[103X -- two inclusions of PathAlgebraMatModules or a list
  of such.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe subrepresentation given by the sum of all the submodules given
            by the inclusions [3Xf, g[103X or [3Xlist[103X.[133X
  
  [33X[0;0YThe  function  checks if [3Xlist[103X is non-empty and if [23X[3Xf[103X\colon M\to X[123X and [23X[3Xg[103X\colon
  N\to  X[123X  or all the homomorphism in [3Xlist[103X have the same range and if they all
  are  inclusions.  If  the  function  is given two arguments [3Xf[103X and [3Xg[103X, then it
  returns  [23X[h,f',g'][123X,  where  [23Xh\colon  M  +  N\to  X[123X,  [23Xf'\colon M\to M + N[123X and
  [23Xg'\colon N\to M + N[123X. For a list of inclusions it returns a monomorphism from
  a module isomorphic to the sum of the subrepresentations to [23XX[123X.[133X
  
  [1X6.4-43 SupportModuleElement[101X
  
  [33X[1;0Y[29X[2XSupportModuleElement[102X( [3Xm[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xm[103X -- an element of a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  primitive  idempotents [3Xv[103X in the algebra over which the module
            containing the element [3Xm[103X is a module, such that [3Xm^v[103X is non-zero.[133X
  
  [33X[0;0YThe  function  checks  if [3Xm[103X is an element in a module over a (quotient of a)
  path algebra, and returns fail otherwise.[133X
  
  [1X6.4-44 TopOfModule[101X
  
  [33X[1;0Y[29X[2XTopOfModule[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X or [3Xf[103X -- a path algebra module or a homomorphism thereof.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  top of the module [3XM[103X or the homomorphism induced on the top of
            the modules associated to the homomorphism [3Xf[103X.[133X
  
  [33X[0;0YThis returns only the representation given by the top of the module [3XM[103X or the
  homomorphism  induced  on  the  top of the modules associated to the entered
  homomorphism.  The  operation  [2XTopOfModuleProjection[102X  ([14X7.3-28[114X)  computes the
  projection of the module [3XM[103X onto the top of the module [3XM[103X.[133X
  
  
  [1X6.5 [33X[0;0YSpecial representations[133X[101X
  
  [33X[0;0YHere  we  collect  the  predefined  representations/modules  over  a  finite
  dimensional quotient of a path algebra.[133X
  
  [1X6.5-1 BasisOfProjectives[101X
  
  [33X[1;0Y[29X[2XBasisOfProjectives[102X( [3XA[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XA[103X -- a finite dimensional (quotient of a) path algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ya   list   of   bases   for   all  the  indecomposable  projective
            representations   over   [3XA[103X.  The  basis  for  each  indecomposable
            projective is given a list of elements in nontips in [3XA[103X.[133X
  
  [33X[0;0YThe function checks if the algebra [3XA[103X is a finite dimensional (quotient of a)
  path algebra, and returns an error message otherwise.[133X
  
  [1X6.5-2 ElementInIndecProjective[101X
  
  [33X[1;0Y[29X[2XElementInIndecProjective[102X( [3XA[103X, [3Xm[103X, [3Xs[103X ) [32X operation[133X
  
  [33X[0;0YArguments:  [3XA[103X  --  a  QuiverAlgebra,  [3Xm[103X  --  an element in an indecomposable
  projective representation, [3Xs[103X -- an integer.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  element  in  the path algebra corresponding to [3Xm[103X in the right
            ideal  from  which the indecomposable projective representation is
            constructed.[133X
  
  [1X6.5-3 IndecInjectiveModules[101X
  
  [33X[1;0Y[29X[2XIndecInjectiveModules[102X( [3XA[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XA[103X -- a finite dimensional (quotient of a) path algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ya   list   of  all  the  non-isomorphic  indecomposable  injective
            representations over [3XA[103X.[133X
  
  [33X[0;0YThe function checks if the algebra [3XA[103X is a finite dimensional (quotient of a)
  path algebra, and returns an error message otherwise.[133X
  
  [1X6.5-4 IndecProjectiveModules[101X
  
  [33X[1;0Y[29X[2XIndecProjectiveModules[102X( [3XA[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XA[103X -- a finite dimensional (quotient of a) path algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ya   list  of  all  the  non-isomorphic  indecomposable  projective
            representations over [3XA[103X.[133X
  
  [33X[0;0YThe function checks if the algebra [3XA[103X is a finite dimensional (quotient of a)
  path algebra, and returns an error message otherwise.[133X
  
  [1X6.5-5 SimpleModules[101X
  
  [33X[1;0Y[29X[2XSimpleModules[102X( [3XA[103X ) [32X attribute[133X
  
  [33X[0;0YArguments:  [3XA[103X  --  a  finite  dimensional  (admissible  quotient  of a) path
  algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ya list of all the simple representations over [3XA[103X .[133X
  
  [33X[0;0YThe  function  checks  if  the algebra [3XA[103X is a finite dimensional (admissible
  quotient of a) path algebra, and returns an error message otherwise.[133X
  
  [1X6.5-6 ZeroModule[101X
  
  [33X[1;0Y[29X[2XZeroModule[102X( [3XA[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XA[103X -- a finite dimensional (quotient of a) path algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe zero representation over [3XA[103X.[133X
  
  [33X[0;0YThe function checks if the algebra [3XA[103X is a finite dimensional (quotient of a)
  path algebra, and returns an error message otherwise.[133X
  
  
  [1X6.6 [33X[0;0YFunctors on representations[133X[101X
  
  [1X6.6-1 DualOfModule[101X
  
  [33X[1;0Y[29X[2XDualOfModule[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a [10XPathAlgebraMatModule[110X.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  dual  of  [3XM[103X  over the opposite algebra [22XA^op[122X, if [3XM[103X is a module
            over [22XA[122X.[133X
  
  [1X6.6-2 DualOfModuleHomomorphism[101X
  
  [33X[1;0Y[29X[2XDualOfModuleHomomorphism[102X( [3Xf[103X ) [32X attribute[133X
  
  [33X[0;0YArguments:  [3Xf[103X  --  a  map  between  two  representations [3XM[103X and [3XN[103X over a path
  algebra [23XA[123X.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe dual of this map over the opposite path algebra [3XA^\op[103X.[133X
  
  [1X6.6-3 DTr[101X
  
  [33X[1;0Y[29X[2XDTr[102X( [3XM[103X[, [3Xn[103X] ) [32X operation[133X
  [33X[1;0Y[29X[2XDualOfTranspose[102X( [3XM[103X[, [3Xn[103X] ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module, (optional) [3Xn[103X -- an integer.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe dual of the transpose of [3XM[103X when called with only one argument,
            while  it  returns  the dual of the transpose applied to [3XM[103X [3Xn[103X times
            otherwise.  If  [3Xn[103X  is  negative,  then powers of [10XTrD[110X are computed.
            [2XDualOfTranspose[102X is a synonym for [2XDTr[102X.[133X
  
  [1X6.6-4 DTr[101X
  
  [33X[1;0Y[29X[2XDTr[102X( [3Xf[103X[, [3Xn[103X] ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xf[103X -- a path algebra module homomorphism and [3Xn[103X -- an integer.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe [3Xn[103X-th power of the dual of the transpose of the homomorphism [3Xf[103X.[133X
  
  [1X6.6-5 NakayamaFunctorOfModule[101X
  
  [33X[1;0Y[29X[2XNakayamaFunctorOfModule[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a [10XPathAlgebraMatModule[110X.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  module [22XHom_K(Hom_A(M,A), K)[122X over [22XA[122X, when [3XM[103X is a module over a
            [22XK[122X-algebra [22XA[122X.[133X
  
  [1X6.6-6 NakayamaFunctorOfModuleHomomorphism[101X
  
  [33X[1;0Y[29X[2XNakayamaFunctorOfModuleHomomorphism[102X( [3Xf[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3Xf[103X -- a map between two modules [3XM[103X and [3XN[103X over a path algebra [23XA[123X.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe   homomorphism   induced   by   [22Xf:   M->  N[122X  from  the  module
            [22XHom_K(Hom_A(M,A),K)[122X  to  [22XHom_K(Hom_A(N,A),  K)[122X, when [3Xf[103X is a module
            homomorphism over a [22XK[122X-algebra [3XA[103X.[133X
  
  [1X6.6-7 OppositeNakayamaFunctorOfModule[101X
  
  [33X[1;0Y[29X[2XOppositeNakayamaFunctorOfModule[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a [10XPathAlgebraMatModule[110X.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  module [22XHom_A(Hom_K(M,K), A)[122X over [22XA[122X, when [3XM[103X is a module over a
            [22XK[122X-algebra [22XA[122X.[133X
  
  [1X6.6-8 OppositeNakayamaFunctorOfModuleHomomorphism[101X
  
  [33X[1;0Y[29X[2XOppositeNakayamaFunctorOfModuleHomomorphism[102X( [3Xf[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3Xf[103X -- a map between two modules [3XM[103X and [3XN[103X over a path algebra [23XA[123X.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe   homomorphism   induced   by   [22Xf:   M->  N[122X  from  the  module
            [22XHom_A(Hom_K(M,K),A)[122X  to  [22XHom_A(Hom_K(N,K),  A)[122X, when [3Xf[103X is a module
            homomorphism over a [22XK[122X-algebra [3XA[103X.[133X
  
  [1X6.6-9 RestrictionViaAlgebraHomomorphism[101X
  
  [33X[1;0Y[29X[2XRestrictionViaAlgebraHomomorphism[102X( [3Xf[103X, [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xf[103X -- an IsAlgebraHomomorphism, [3XM[103X -- an IsPathAlgebraMatModule.[133X
  
  [6XReturns:[106X  [33X[0;10YGiven  an  algebra  homomorphism  [22Xf : A ↪ B[122X and a module [3XM[103X over [22XB[122X,
            this function returns [3XM[103X as a module over [22XA[122X.[133X
  
  [1X6.6-10 RestrictionViaAlgebraHomomorphismMap[101X
  
  [33X[1;0Y[29X[2XRestrictionViaAlgebraHomomorphismMap[102X( [3Xf[103X, [3Xh[103X ) [32X operation[133X
  
  [33X[0;0YArguments:     [3Xf[103X     --     an     IsAlgebraHomomorphism,     [3Xh[103X     --    an
  IsPathAlgebraMatModuleHomomorphism.[133X
  
  [6XReturns:[106X  [33X[0;10YGiven  an  algebra  homomorphism  [22Xf  : A ↪ B[122X and a homomorphism of
            modules  [3Xh[103X  from  [22XM[122X to [22XN[122X over [22XB[122X, this function returns the induced
            homomorphism induced by [3Xh[103X as a homomorphism over [22XA[122X.[133X
  
  [1X6.6-11 StarOfModule[101X
  
  [33X[1;0Y[29X[2XStarOfModule[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a [10XPathAlgebraMatModule[110X.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  module  [22XHom_A(M,A)[122X over the opposite of [22XA[122X, when [3XM[103X is a module
            over an algebra [22XA[122X.[133X
  
  [1X6.6-12 StarOfModuleHomomorphism[101X
  
  [33X[1;0Y[29X[2XStarOfModuleHomomorphism[102X( [3Xf[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3Xf[103X -- a map between two modules [3XM[103X and [3XN[103X over a path algebra [23XA[123X.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe homomorphism induced by [22Xf: M-> N[122X from the module [22XHom_A(N,A)[122X to
            [22XHom_A(M,A)[122X, when [3Xf[103X is a module homomorphism over an algebra [3XA[103X.[133X
  
  [1X6.6-13 TensorProductOfModules[101X
  
  [33X[1;0Y[29X[2XTensorProductOfModules[102X( [3XM[103X, [3XN[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X, [3XN[103X -- two path algebra modules[133X
  
  [6XReturns:[106X  [33X[0;10Ythe tensor product [22XM⊗_A N[122X as a vector space and a function [22XM× N ->
            M⊗_A  N[122X,  given  two  representations  [3XM[103X and [3XN[103X, where [3XM[103X is a right
            module over [22XA[122X and [3XN[103X is a right module over the opposite of [22XA[122X.[133X
  
  [1X6.6-14 TrD[101X
  
  [33X[1;0Y[29X[2XTrD[102X( [3XM[103X[, [3Xn[103X] ) [32X operation[133X
  [33X[1;0Y[29X[2XTransposeOfDual[102X( [3XM[103X[, [3Xn[103X] ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module, (optional) [3Xn[103X -- an integer.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe transpose of the dual of [3XM[103X when called with only one argument,
            while  it  returns  the transpose of the dual applied to [3XM[103X [3Xn[103X times
            otherwise.  If  [3Xn[103X  is  negative,  then powers of [10XTrD[110X are computed.
            [2XTransposeOfDual[102X is a synonym for [2XTrD[102X.[133X
  
  [1X6.6-15 TrD[101X
  
  [33X[1;0Y[29X[2XTrD[102X( [3Xf[103X[, [3Xn[103X] ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xf[103X -- a path algebra module homomorphism, [3Xn[103X -- an integer.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe [3Xn[103X-th power of the transpose of the dual of the homomorphism [3Xf[103X.[133X
  
  [1X6.6-16 TransposeOfModule[101X
  
  [33X[1;0Y[29X[2XTransposeOfModule[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a path algebra module.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe transpose of the module [3XM[103X.[133X
  
  [1X6.6-17 TransposeOfModuleHomomorphism[101X
  
  [33X[1;0Y[29X[2XTransposeOfModuleHomomorphism[102X( [3Xf[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3Xf[103X -- a path algebra module homomorphism.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe transpose of the module homomorphism [3Xf[103X.[133X
  
  
  [1X6.7 [33X[0;0YVertex projective modules and submodules thereof[133X[101X
  
  [33X[0;0YIn  general,  if  [23XR[123X  is  a  ring  and  [23Xe[123X is an idempotent of [23XR[123X, then [23XeR[123X is a
  projective  module  of  [23XR[123X. Then we can form a direct sum of these projective
  modules  together  to  form larger projective module. One can construct more
  general modules by providing a [3Xvertex projective presentation[103X. In this case,
  [23XM[123X is the cokernel as given by the following exact sequence: [23X\oplus_{j=1}^{r}
  w(j)R  \rightarrow  \oplus_{i=1}^{g}  v(i)R \rightarrow{M} \rightarrow 0[123X for
  some map between [23X\oplus_{j=1}^{r} w(j)R[123X and [23X\oplus_{i=1}^{g} v(i)R[123X. The maps
  [23Xw[123X and [23Xv[123X map the integers to some idempotent in [23XR[123X.[133X
  
  [1X6.7-1 RightProjectiveModule[101X
  
  [33X[1;0Y[29X[2XRightProjectiveModule[102X( [3XA[103X, [3Xverts[103X ) [32X function[133X
  
  [33X[0;0YArguments: [3XA[103X -- a (quotient of a) path algebra, [3Xverts[103X -- a list of vertices.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe  right  projective  module  over  [3XA[103X which is the direct sum of
            projective  modules  of  the  form [3XvA[103X where the vertices are taken
            from [3Xverts[103X.[133X
  
  [33X[0;0YThe   module  created  is  in  the  category  [10XIsPathAlgebraModule[110X.  In  this
  implementation  the  algebra  can be a quotient of a path algebra. So if the
  list  was [23X[v,w][123X then the module created will be the direct sum [23XvA \oplus wA[123X,
  in  that order. Elements of the modules are vectors of algebra elements, and
  in  each component, each path begins with the vertex in that position in the
  list  of  vertices.  Right  projective  modules are implementated as algebra
  modules  (see [14XReference: Representations of Algebras[114X) and all operations for
  algebra  modules  are applicable to right projective modules. In particular,
  one    can   construct   submodules   using   [2XSubAlgebraModule[102X   ([14XReference:
  SubAlgebraModule[114X).[133X
  
  [33X[0;0YHere we create the right projective module [23XP = vA \oplus vA \oplus wA[123X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XF := GF(11);[127X[104X
    [4X[28XGF(11)[128X[104X
    [4X[25Xgap>[125X [27XQ := Quiver(["v","w", "x"],[["v","w","a"],["v","w","b"],[127X[104X
    [4X[25X>[125X [27X["w","x","c"]]);[127X[104X
    [4X[28X<quiver with 3 vertices and 3 arrows>[128X[104X
    [4X[25Xgap>[125X [27XA := PathAlgebra(F,Q);[127X[104X
    [4X[28X<GF(11)[<quiver with 3 vertices and 3 arrows>]>[128X[104X
    [4X[25Xgap>[125X [27XP := RightProjectiveModule(A,[A.v,A.v,A.w]);[127X[104X
    [4X[28X<right-module over <GF(11)[<quiver with 3 vertices and 3 arrows>]>>[128X[104X
    [4X[25Xgap>[125X [27XDimension(P);[127X[104X
    [4X[28X12 [128X[104X
  [4X[32X[104X
  
  [1X6.7-2 CompletelyReduceGroebnerBasisForModule[101X
  
  [33X[1;0Y[29X[2XCompletelyReduceGroebnerBasisForModule[102X( [3XGB[103X ) [32X function[133X
  
  [33X[0;0YArguments:  [3XGB[103X  --  an  right  Groebner  basis for a (submodule of a) vertex
  projective module over a path algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  completely  reduced  right  Groebner  basis  from  the  entered
            Groebner basis [3XGB[103X.[133X
  
  [33X[0;0YThis function takes as input an right Groebner basis for a vertex projective
  module  or  a  submodule  thereof,  an  constructs  completely reduced right
  Groebner from it.[133X
  
  [1X6.7-3 IsLeftDivisible[101X
  
  [33X[1;0Y[29X[2XIsLeftDivisible[102X( [3Xx[103X, [3Xy[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3Xx, y[103X -- two path algebra vectors.[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if the tip of [3Xy[103X left divides the tip of [3Xx[103X. False otherwise.[133X
  
  [33X[0;0YGiven  two  PathAlgebraVectors  [3Xx[103X and [3Xy[103X, then [3Xy[103X is said to left divide [3Xx[103X, if
  the  tip  of  [3Xx[103X  and  the  tip  of  [3Xy[103X  occur in the same coordinate, and the
  tipmonomial of the tip of [3Xy[103X leftdivides the tipmonomial of the tip of [3Xx[103X.[133X
  
  [1X6.7-4 IsPathAlgebraModule[101X
  
  [33X[1;0Y[29X[2XIsPathAlgebraModule[102X( [3XP[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3XP[103X -- any object.[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue if the argument [3XP[103X is in the category [10XIsPathAlgebraModule[110X.[133X
  
  [1X6.7-5 IsPathAlgebraVector[101X
  
  [33X[1;0Y[29X[2XIsPathAlgebraVector[102X( [3Xv[103X ) [32X property[133X
  
  [33X[0;0YArguments: [3Xv[103X -- a path algebra vector.[133X
  
  [6XReturns:[106X  [33X[0;10Ytrue  if  [3Xv[103X has been constructed as a PathAlgebraVector. Otherwise
            it returns false.[133X
  
  [1X6.7-6 LeadingCoefficient (of PathAlgebraVector)[101X
  
  [33X[1;0Y[29X[2XLeadingCoefficient (of PathAlgebraVector)[102X( [3Xx[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xx[103X -- an element in a PathAlgebraModule.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe coefficient of the leading term/tip of a [10XPathAlgebraVector[110X.[133X
  
  [33X[0;0YThe  tip  of  the element [3Xx[103X can by found by applying the command [2XLeadingTerm
  (of PathAlgebraVector)[102X ([14X6.7-9[114X).[133X
  
  [1X6.7-7 LeadingComponent[101X
  
  [33X[1;0Y[29X[2XLeadingComponent[102X( [3Xv[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xv[103X -- a path algebra vector.[133X
  
  [6XReturns:[106X  [33X[0;10Y[10Xv[pos][110X,  where  [10Xpos[110X  is  the coordinate for the tip of the vector,
            whenever  [3Xv[103X is non-zero. That is, it returns the coordinate of the
            vector [3Xv[103X where the tip occors. It returns zero otherwise.[133X
  
  [1X6.7-8 LeadingPosition[101X
  
  [33X[1;0Y[29X[2XLeadingPosition[102X( [3Xv[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xv[103X -- a path algebra vector.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe coordinate in which the tip of the vector occurs.[133X
  
  [1X6.7-9 LeadingTerm (of PathAlgebraVector)[101X
  
  [33X[1;0Y[29X[2XLeadingTerm (of PathAlgebraVector)[102X( [3Xx[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xx[103X -- an element in a PathAlgebraModule.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe leading term/tip of a [10XPathAlgebraVector[110X.[133X
  
  [33X[0;0YThe  tip  of the element [3Xx[103X is computed using the following order: the tip is
  computed  for  each  coordinate,  if  the largest of these occur as a tip of
  several  coordinates,  then the coordinate with the smallest index from 1 to
  the  length  of  vector is chosen. The position of the tip was computed when
  the [10XPathAlgebraVector[110X was created.[133X
  
  [1X6.7-10 LeftDivision[101X
  
  [33X[1;0Y[29X[2XLeftDivision[102X( [3Xx[103X, [3Xy[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xx, y[103X -- two path algebra vectors.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  scalar  multiple  of  a path, say [23X\lambda[123X such that the tips of
            [23Xy*\lambda[123X and [23Xx[123X are the same, if the tip of [3Xy[103X left divides the tip
            of [3Xx[103X. False otherwise.[133X
  
  [33X[0;0YIn  the  following  example,  we  create  two  elements  in  [23XP[123X, perform some
  elementwise  operations,  and  then  construct  a  submodule  using  the two
  elements as generators.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xp1 := Vectorize(P,[A.b*A.c,A.a*A.c,A.c]);[127X[104X
    [4X[28X[ (Z(11)^0)*b*c, (Z(11)^0)*a*c, (Z(11)^0)*c ][128X[104X
    [4X[25Xgap>[125X [27Xp2 := Vectorize(P,[A.a,A.b,A.w]);[127X[104X
    [4X[28X[ (Z(11)^0)*a, (Z(11)^0)*b, (Z(11)^0)*w ][128X[104X
    [4X[25Xgap>[125X [27X2*p1 + p2;[127X[104X
    [4X[28X[ (Z(11)^0)*a+(Z(11))*b*c, (Z(11)^0)*b+(Z(11))*a*c, [128X[104X
    [4X[28X  (Z(11)^0)*w+(Z(11))*c ][128X[104X
    [4X[25Xgap>[125X [27XS := SubAlgebraModule(P,[p1,p2]);[127X[104X
    [4X[28X<right-module over <GF(11)[<quiver with 3 vertices and 3 arrows>]>>[128X[104X
    [4X[25Xgap>[125X [27XDimension(S);[127X[104X
    [4X[28X3 [128X[104X
  [4X[32X[104X
  
  [1X6.7-11 ^[101X
  
  [33X[1;0Y[29X[2X^[102X( [3Xm[103X, [3Xa[103X ) [32X operation[133X
  
  [33X[0;0YArguments:  [3Xm[103X  --  an element of a path algebra module, [3Xa[103X -- an element of a
  path algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe element [3Xm[103X multiplied with [3Xa[103X.[133X
  
  [33X[0;0YThis action is defined by multiplying each component in [3Xm[103X by [3Xa[103X on the right.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xp2^(A.c - A.w);[127X[104X
    [4X[28X[ (Z(11)^5)*a+(Z(11)^0)*a*c, (Z(11)^5)*b+(Z(11)^0)*b*c, [128X[104X
    [4X[28X  (Z(11)^5)*w+(Z(11)^0)*c ] [128X[104X
  [4X[32X[104X
  
  [1X6.7-12 <[101X
  
  [33X[1;0Y[29X[2X<[102X( [3Xm1[103X, [3Xm2[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xm1, m2[103X -- two elements of a PathAlgebraModule.[133X
  
  [6XReturns:[106X  [33X[0;10Y`true' if [3Xm1[103X is less than [3Xm2[103X and false otherwise.[133X
  
  [33X[0;0YElements are compared componentwise from left to right using the ordering of
  the  underlying  algebra.  The  element [3Xm1[103X is less than [3Xm2[103X if the first time
  components are not equal, the component of [3Xm1[103X is less than the corresponding
  component of [3Xm2[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xp1 < p2;[127X[104X
    [4X[28Xfalse [128X[104X
  [4X[32X[104X
  
  [1X6.7-13 /[101X
  
  [33X[1;0Y[29X[2X/[102X( [3XM[103X, [3XN[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3XM, N[103X -- two finite dimensional [10XPathAlgebraModule[110Xs.[133X
  
  [6XReturns:[106X  [33X[0;10Ythe factor module [23XM/N[123X.[133X
  
  [33X[0;0YThis  module is again a right algebra module, and all applicable methods and
  operations  are  available for the resulting factor module. Furthermore, the
  resulting  module  is  a vector space, so operations for computing bases and
  dimensions are also available.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XPS := P/S;[127X[104X
    [4X[28X<9-dimensional right-module over <GF(11)[<quiver with 3 vertices and [128X[104X
    [4X[28X3 arrows>]>>[128X[104X
    [4X[25Xgap>[125X [27XBasis(PS);[127X[104X
    [4X[28XBasis( <9-dimensional right-module over <GF(11)[<quiver with [128X[104X
    [4X[28X3 vertices and 3 arrows>]>>, [128X[104X
    [4X[28X[ [ [ <zero> of ..., (Z(11)^0)*v, <zero> of ... ] ], [128X[104X
    [4X[28X  [ [ (Z(11)^0)*v, <zero> of ..., <zero> of ... ] ], [128X[104X
    [4X[28X  [ [ <zero> of ..., <zero> of ..., (Z(11)^0)*w ] ], [128X[104X
    [4X[28X  [ [ <zero> of ..., (Z(11)^0)*a, <zero> of ... ] ], [128X[104X
    [4X[28X  [ [ (Z(11)^0)*a, <zero> of ..., <zero> of ... ] ], [128X[104X
    [4X[28X  [ [ (Z(11)^0)*b, <zero> of ..., <zero> of ... ] ], [128X[104X
    [4X[28X  [ [ <zero> of ..., <zero> of ..., (Z(11)^0)*c ] ], [128X[104X
    [4X[28X  [ [ <zero> of ..., (Z(11)^0)*a*c, <zero> of ... ] ], [128X[104X
    [4X[28X  [ [ (Z(11)^0)*a*c, <zero> of ..., <zero> of ... ] ] ] ) [128X[104X
  [4X[32X[104X
  
  [1X6.7-14 PathAlgebraVector[101X
  
  [33X[1;0Y[29X[2XPathAlgebraVector[102X( [3Xfam[103X, [3Xcomponents[103X ) [32X operation[133X
  
  [33X[0;0YArguments:  [3Xfam[103X  --  a  PathAlgebraVectorFamily, [3Xcomponents[103X -- a homogeneous
  list of elements.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  PathAlgebraVector  in  the PathAlgebraVectorFamily [3Xfam[103X with the
            components of the vector being equal to [3Xcomponents[103X.[133X
  
  [33X[0;0YThis  function  is  typically  used  when  constructing elements of a module
  constructed  by  the  command  [10XRightProjectiveModule[110X. If [10XP[110X is constructed as
  say,   [10XP   :=   RightProjectiveModule(KQ,   [KQ.v1,   KQ.v1,  KQ.v2])[110X,  then
  [10XExtRepOfObj(p)[110X,  where  [10Xp[110X is an element if [10XP[110X is a [10XPathAlgebraVector[110X. The tip
  is  computed  using  the  following  ordering:  the tip is computed for each
  coordinate,  if  the largest of these occur as a tip of several coordinates,
  then  the  coordinate with the smallest index from 1 to the length of vector
  is chosen.[133X
  
  [1X6.7-15 ProjectivePathAlgebraPresentation[101X
  
  [33X[1;0Y[29X[2XProjectivePathAlgebraPresentation[102X( [3XM[103X ) [32X operation[133X
  
  [33X[0;0YArguments:  [3XM[103X  --  a  finite  dimensional module over a (quotient of a) path
  algebra.[133X
  
  [6XReturns:[106X  [33X[0;10Ya projective presentation of the entered module [3XM[103X over a (qoutient
            of  a)  path algebra [23XA[123X. The projective presentation, or resolution
            is over the path algebra form which [23XA[123X was constructed.[133X
  
  [33X[0;0YThis  function  takes  as  input  a  PathAlgebraMatModule  and  constructs a
  projetive presentation of this module over the path algebra over which it is
  defined,  ie.  a projetive resolution of length 1. It returns a list of five
  elements:  (1) a projective module [23XP[123X over the path algebra, which modulo the
  relations  induced  the  projective  cover of [3XM[103X, (2) a submodule [23XU[123X of [23XP[123X such
  that  [23XP/U[123X  is  isomorphic  to  [3XM[103X,  (3)  module  generators  of [23XP[123X, (4) module
  generators  for  [23XU[123X which forms a completely reduced right Groebner basis for
  [23XU[123X,  and  (5)  a matrix with enteries in the path algebra which gives the map
  from  [23XU[123X to [23XP[123X, if [23XU[123X were considered a direct sum of vertex projective modules
  over the path algebra.[133X
  
  [1X6.7-16 RightGroebnerBasisOfModule[101X
  
  [33X[1;0Y[29X[2XRightGroebnerBasisOfModule[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a PathAlgebraModule.[133X
  
  [6XReturns:[106X  [33X[0;10Ya right Groebner basis for the module [3XM[103X.[133X
  
  [33X[0;0YIt  checks  if  the acting algebra on the module [3XM[103X is a path algebra, and it
  returns an error message otherwise. The elements in the right Groebner basis
  that  is  constructed,  can  be  retrieved  by the command [10XBasisVectors[110X. The
  underlying  module is likewise returned by the command [10XUnderlyingModule[110X. The
  output    of    the    function    is    satisfying    the   filter/category
  [10XIsRightPathAlgebraModuleGroebnerBasis[110X.[133X
  
  [1X6.7-17 TargetVertex[101X
  
  [33X[1;0Y[29X[2XTargetVertex[102X( [3Xv[103X ) [32X operation[133X
  
  [33X[0;0YArguments: [3Xv[103X -- a PathAlgebraVector.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  vertex  [23Xw[123X  such that [23Xv*w = v[123X, if such a vertex exists, and fail
            otherwise.[133X
  
  [33X[0;0YGiven  a PathAlgebraVector [3Xv[103X, if [3Xv[103X is right uniform, this function finds the
  vertex [23Xw[123X such that [23Xv*w = v[123X whenever [3Xv[103X is non-zero, and returns the zero path
  otherwise. If [3Xv[103X is not right uniform it returns fail.[133X
  
  [1X6.7-18 UniformGeneratorsOfModule[101X
  
  [33X[1;0Y[29X[2XUniformGeneratorsOfModule[102X( [3XM[103X ) [32X attribute[133X
  
  [33X[0;0YArguments: [3XM[103X -- a [10XPathAlgebraModule[110X.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  set  of  right  uniform generators of the mdoule [3XM[103X. If [3XM[103X is the
            zero module, then it returns an empty list.[133X
  
  [1X6.7-19 Vectorize[101X
  
  [33X[1;0Y[29X[2XVectorize[102X( [3XM[103X, [3Xcomponents[103X ) [32X function[133X
  
  [33X[0;0YArguments:  [3XM[103X  --  a  module  over  a  path algebra, [3Xcomponents[103X -- a list of
  elements of [3XM[103X.[133X
  
  [6XReturns:[106X  [33X[0;10Ya  vector  in  [3XM[103X  from a list of path algebra elements [3Xcomponents[103X,
            which defines the components in the resulting vector.[133X
  
  [33X[0;0YThe  returned vector is normalized, so the vector's components may not match
  the input components.[133X
  
