  
  [1X5 [33X[0;0YMatrices[133X[101X
  
  [33X[0;0YA  compressed  matrix  (a  [10Xcmat[110X)  behaves  very  much  like a list of [10Xcvec[110Xs.
  However,  it  insists  on  having only [10Xcvec[110Xs of the same length and over the
  same  base  field  as  its  elements, and it insists on being a list without
  holes.  Apart  from  these  restrictions,  you can use all the standard list
  operations with [10Xcmat[110Xs (see Section [14X5.2[114X.[133X
  
  [33X[0;0YIn  the  rest  of this chapter, we document all methods for matrices for the
  sake  of  completeness.  If  they behave exactly as is to be expected by the
  already defined operation no further explanation is given.[133X
  
  
  [1X5.1 [33X[0;0YCreation[133X[101X
  
  [33X[0;0YThe  basic  operation  to  create  new [10Xcmat[110Xs is [11XCMat[111X, for which a variety of
  methods is available:[133X
  
  [1X5.1-1 CMat[101X
  
  [29X[2XCMat[102X( [3Xl[103X, [3Xcl[103X, [3Xdochecks[103X ) [32X method
  [29X[2XCMat[102X( [3Xl[103X, [3Xcl[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya new [10Xcmat[110X[133X
  
  [33X[0;0YA  new  [10Xcmat[110X is created with rows being in the [10Xcvecclass[110X [3Xcl[103X. All elements of
  the list [3Xl[103X must be [10Xcvec[110Xs in that class. The boolean flag [3Xdochecks[103X indicates,
  whether  this  should  be checked or not. If the flag is omitted, checks are
  performed. Note that [3Xl[103X may be the empty list.[133X
  
  [1X5.1-2 CMat[101X
  
  [29X[2XCMat[102X( [3Xl[103X, [3Xdochecks[103X ) [32X method
  [29X[2XCMat[102X( [3Xl[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya new [10Xcmat[110X[133X
  
  [33X[0;0YA  new [10Xcmat[110X is created with rows being in the [10Xcvecclass[110X of the vectors in [3Xl[103X.
  All elements of the list [3Xl[103X must be [10Xcvec[110Xs in the same class. The boolean flag
  [3Xdochecks[103X  indicates,  whether  this should be checked or not. If the flag is
  omitted, checks are performed. Note that [3Xl[103X may not be the empty list.[133X
  
  [1X5.1-3 CMat[101X
  
  [29X[2XCMat[102X( [3Xl[103X, [3Xv[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya new [10Xcmat[110X[133X
  
  [33X[0;0YA  new  [10Xcmat[110X  is created with rows being in the [10Xcvecclass[110X of the [10Xcvec[110X [3Xv[103X. All
  elements  of  the  list  [3Xl[103X  must  be  [10Xcvec[110Xs  in the that same class. This is
  checked. Note that [3Xl[103X may be the empty list.[133X
  
  [1X5.1-4 CMat[101X
  
  [29X[2XCMat[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya new [10Xcmat[110X[133X
  
  [33X[0;0YCreates a new [10Xcmat[110X which is equal to [3Xm[103X, which must be a compressed matrix in
  the filter [11XIsGF2MatrixRep[111X or the filter [11XIs8BitMatrixRep[111X.[133X
  
  [33X[0;0YThere are some methods to create [10Xcmat[110Xs of special form:[133X
  
  [1X5.1-5 CVEC_ZeroMat[101X
  
  [29X[2XCVEC_ZeroMat[102X( [3Xrows[103X, [3Xcl[103X ) [32X function
  [29X[2XCVEC_ZeroMat[102X( [3Xrows[103X, [3Xcols[103X, [3Xp[103X, [3Xd[103X ) [32X function
  [6XReturns:[106X  [33X[0;10Ya new [10Xcmat[110X[133X
  
  [33X[0;0YCreates  a  zero  matrix  with  [3Xrows[103X  rows  and  [3Xcols[103X columns over the field
  [10XGF([3Xp[103X[10X,[3Xd[103X[10X)[110X.  If  a  [10Xcvecclass[110X  [3Xcl[103X is given, the number of columns and the field
  follow from that.[133X
  
  [1X5.1-6 CVEC_IdentityMat[101X
  
  [29X[2XCVEC_IdentityMat[102X( [3Xcl[103X ) [32X function
  [29X[2XCVEC_IdentityMat[102X( [3Xn[103X, [3Xp[103X, [3Xd[103X ) [32X function
  [6XReturns:[106X  [33X[0;10Ya new [10Xcmat[110X[133X
  
  [33X[0;0YCreates  an  identity matrix with [3Xn[103X rows and columns over the field [10XGF([3Xp[103X[10X,[3Xd[103X[10X)[110X.
  If  a [10Xcvecclass[110X [3Xcl[103X is given, the number of columns and the field follow from
  that.[133X
  
  [1X5.1-7 CVEC_RandomMat[101X
  
  [29X[2XCVEC_RandomMat[102X( [3Xrows[103X, [3Xcl[103X ) [32X function
  [29X[2XCVEC_RandomMat[102X( [3Xrows[103X, [3Xcols[103X, [3Xp[103X, [3Xd[103X ) [32X function
  [6XReturns:[106X  [33X[0;10Ya new [10Xcmat[110X[133X
  
  [33X[0;0YCreates  a  random  matrix  with  [3Xrows[103X  rows and [3Xcols[103X columns over the field
  [10XGF([3Xp[103X[10X,[3Xd[103X[10X)[110X.  If  a  [10Xcvecclass[110X  [3Xcl[103X is given, the number of columns and the field
  follow from that. Note that this is not particularly efficient.[133X
  
  [1X5.1-8 MutableCopyMat[101X
  
  [29X[2XMutableCopyMat[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya mutable copy of [3Xm[103X[133X
  
  [33X[0;0YCreates a mutable copy of the [10Xcmat[110X [3Xm[103X.[133X
  
  [1X5.1-9 Matrix[101X
  
  [29X[2XMatrix[102X( [3Xvectorlist[103X, [3Xvector[103X ) [32X method
  [29X[2XMatrixNC[102X( [3Xvectorlist[103X, [3Xvector[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya new mutable [10Xcmat[110X[133X
  
  [33X[0;0YReturns  a  new  [10Xcmat[110X  containing  the  vectors  in  [3Xvectorlist[103X as rows. The
  elements  in  [3Xvectorlist[103X  must  be  vectors of the same length as the sample
  vector  [3Xvector[103X  and must live over the same base field. The sample vector is
  always  necessary to be able to use the method selection. The [3Xvectorlist[103X may
  be empty. The NC method does not check the inputs.[133X
  
  
  [1X5.2 [33X[0;0YMatrices as lists[133X[101X
  
  [33X[0;0YIn  this  section,  arguments  named [3Xm[103X and [3Xn[103X are [10Xcmat[110Xs and [3Xv[103X and [3Xw[103X are [10Xcvec[110Xs
  that  fit  into  the corresponding matrices. [3Xpos[103X is an integer between [22X1[122X and
  [10XLength(m)[110X if it applies to the matrix [3Xm[103X.[133X
  
  [1X5.2-1 Add[101X
  
  [29X[2XAdd[102X( [3Xm[103X, [3Xv[103X[, [3Xpos[103X] ) [32X method
  [6XReturns:[106X  [33X[0;10Ynothing[133X
  
  [33X[0;0YBehaves  exactly  as expected. Note that one can only add [10Xcvec[110Xs of the right
  length and over the right field.[133X
  
  [1X5.2-2 Remove[101X
  
  [29X[2XRemove[102X( [3Xm[103X[, [3Xpos[103X] ) [32X method
  [6XReturns:[106X  [33X[0;10Ya [10Xcvec[110X[133X
  
  [33X[0;0YBehaves exactly as expected. No holes can be made.[133X
  
  [1X5.2-3 ELM_LIST[101X
  
  [29X[2XELM_LIST[102X( [3Xm[103X, [3Xpos[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya [10Xcvec[110X[133X
  
  [33X[0;0YBehaves  exactly  as  expected.  Note that this method is triggered when one
  uses the (reading) syntax [21X[10Xm[pos][110X[121X.[133X
  
  [1X5.2-4 ASS_LIST[101X
  
  [29X[2XASS_LIST[102X( [3Xm[103X, [3Xpos[103X, [3Xv[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ynothing[133X
  
  [33X[0;0YBehaves exactly as expected. Note that one can only assign to positions such
  that  the  resulting  matrix has no holes. This method is triggered when one
  uses the (assignment) syntax [21X[10Xm[pos] := [110X[121X.[133X
  
  [1X5.2-5 ELMS_LIST[101X
  
  [29X[2XELMS_LIST[102X( [3Xm[103X, [3Xposs[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya sub [10Xcmat[110X[133X
  
  [33X[0;0YBehaves exactly as expected: A new matrix containing a subset of the rows is
  returned.  Note  that  the  row  vectors  are  the  same  [5XGAP[105X objects as the
  corresponding  rows  of  [3Xm[103X.  This  operation  is triggered by the expression
  [3Xm[103X[10X{[3Xposs[103X[10X}[110X.[133X
  
  [1X5.2-6 ASSS_LIST[101X
  
  [29X[2XASSS_LIST[102X( [3Xm[103X, [3Xposs[103X, [3Xvals[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ynothing[133X
  
  [33X[0;0YBehaves exactly as expected. Of course all values in [3Xvals[103X must be [10Xcvec[110Xs over
  the  correct  field  and  the  [10Xcmat[110X  [3Xm[103X must be a dense list afterwards. This
  operation is triggered by the statement [3Xm[103X[10X{[3Xposs[103X[10X} := [3Xvals[103X[10X[110X.[133X
  
  [1X5.2-7 Length[101X
  
  [29X[2XLength[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe number of rows of the [10Xcmat[110X [3Xm[103X[133X
  
  [33X[0;0YBehaves exactly as expected.[133X
  
  [1X5.2-8 ShallowCopy[101X
  
  [29X[2XShallowCopy[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya new matrix containing the same rows than the [10Xcmat[110X [3Xm[103X[133X
  
  [33X[0;0YBehaves  exactly  as expected. Note that the rows of the result are the very
  same [5XGAP[105X objects than the rows of the [10Xcmat[110X [3Xm[103X.[133X
  
  [1X5.2-9 Collected[101X
  
  [29X[2XCollected[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe same as the collected list of the rows of [3Xm[103X[133X
  
  [33X[0;0YBehaves  exactly  as  expected. Just uses the standard [2XCollected[102X ([14XReference:
  Collected[114X) on the list of rows.[133X
  
  [1X5.2-10 DuplicateFreeList[101X
  
  [29X[2XDuplicateFreeList[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya  new  mutable  [10Xcmat[110X  containing  the  rows  of [3Xm[103X with duplicates
            removed[133X
  
  [33X[0;0YBehaves  exactly  as  expected.  Just  uses  the  standard [2XDuplicateFreeList[102X
  ([14XReference: DuplicateFreeList[114X) on the list of rows.[133X
  
  [1X5.2-11 Append[101X
  
  [29X[2XAppend[102X( [3Xm[103X, [3Xn[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ynothing[133X
  
  [33X[0;0YBehaves  exactly  as expected. Of course, the [10Xcmat[110Xs [3Xm[103X and [3Xn[103X must be over the
  same  field  and  have  the  same number of columns. Note that the rows of [3Xn[103X
  themselves (and no copies) will be put into the matrix [3Xm[103X.[133X
  
  [1X5.2-12 Filtered[101X
  
  [29X[2XFiltered[102X( [3Xm[103X, [3Xf[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya new [10Xcmat[110X containing some of the rows of [3Xm[103X[133X
  
  [33X[0;0YBehaves  exactly  as expected. The function [3Xf[103X will be called for each row of
  [3Xm[103X.[133X
  
  [1X5.2-13 Unbind[101X
  
  [29X[2XUnbind[102X( [3Xm[103X, [3Xf[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ynothing[133X
  
  [33X[0;0YBehaves  exactly  as  expected.  Of  course,  only the last bound row may be
  unbound.[133X
  
  
  [1X5.3 [33X[0;0YArithmetic[133X[101X
  
  [33X[0;0YOf  course, the standard arithmetic infix operations [22X+[122X, [22X-[122X and [22X*[122X (for vectors
  and  scalars)  work  as expected by using the methods below. The comments on
  the  usage  of  scalars  in  arithmetic  operations  involving  vectors from
  Subsection [14X4.2-1[114X apply analogously.[133X
  
  [1X5.3-1 \+[101X
  
  [29X[2X\+[102X( [3Xm[103X, [3Xn[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe sum [22X[3Xm[103X+[3Xn[103X[122X as a new [10Xcmat[110X[133X
  
  [33X[0;0YFor two [10Xcmat[110Xs [3Xm[103X and [3Xn[103X. Works as expected.[133X
  
  [1X5.3-2 \-[101X
  
  [29X[2X\-[102X( [3Xm[103X, [3Xn[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe difference [22X[3Xm[103X-[3Xn[103X[122X as a new [10Xcmat[110X[133X
  
  [33X[0;0YFor two [10Xcmat[110Xs [3Xm[103X and [3Xn[103X. Works as expected.[133X
  
  [1X5.3-3 AdditiveInverseSameMutability[101X
  
  [29X[2XAdditiveInverseSameMutability[102X( [3Xm[103X ) [32X method
  [29X[2X\-[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe additive inverse of [3Xm[103X as a new [10Xcmat[110X[133X
  
  [33X[0;0YFor a [10Xcmat[110X [3Xm[103X. Works as expected.[133X
  
  [1X5.3-4 AdditiveInverseMutable[101X
  
  [29X[2XAdditiveInverseMutable[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe additive inverse of [3Xm[103X as a new mutable [10Xcmat[110X[133X
  
  [33X[0;0YFor a [10Xcmat[110X [3Xm[103X. Works as expected.[133X
  
  [1X5.3-5 \*[101X
  
  [29X[2X\*[102X( [3Xm[103X, [3Xs[103X ) [32X method
  [29X[2X\*[102X( [3Xs[103X, [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe scalar multiple [3Xs[103X[22X⋅[122X[3Xm[103X[133X
  
  [33X[0;0YFor  a  [10Xcmat[110X [3Xm[103X and a scalar [3Xs[103X. For the format of the scalar see [14X4.2-1[114X. Works
  as expected.[133X
  
  [1X5.3-6 \*[101X
  
  [29X[2X\*[102X( [3Xv[103X, [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe product [3Xv[103X[22X⋅[122X[3Xm[103X[133X
  
  [33X[0;0YFor  a  [10Xcmat[110X [3Xm[103X and a [10Xcvec[110X [3Xs[103X with the same length as the number of rows of [3Xm[103X.
  Works as expected. Note that there is a very fast method for the case that [3Xm[103X
  is pre-greased (see [14X5.8[114X).[133X
  
  [1X5.3-7 \^[101X
  
  [29X[2X\^[102X( [3Xv[103X, [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe product [3Xv[103X[22X⋅[122X[3Xm[103X[133X
  
  [33X[0;0YFor  a  [10Xcmat[110X [3Xm[103X and a [10Xcvec[110X [3Xs[103X with the same length as the number of rows of [3Xm[103X.
  Works as expected. Note that there is a very fast method for the case that [3Xm[103X
  is pre-greased (see [14X5.8[114X).[133X
  
  [1X5.3-8 \*[101X
  
  [29X[2X\*[102X( [3Xm[103X, [3Xn[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe product [3Xm[103X[22X⋅[122X[3Xn[103X[133X
  
  [33X[0;0YOf  course,  the  [10Xcmat[110X  [3Xm[103X  must have as many columns as the [10Xcmat[110X [3Xn[103X has rows.
  Works as expected. Note that there is a very fast method for the case that [3Xn[103X
  is pre-greased (see [14X5.8[114X).[133X
  
  [1X5.3-9 ZeroSameMutability[101X
  
  [29X[2XZeroSameMutability[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe  zero [10Xcmat[110X over the same field and with the same dimensions as
            [3Xm[103X[133X
  
  [33X[0;0Y[3Xm[103X must be a [10Xcmat[110X.[133X
  
  [1X5.3-10 ZeroMutable[101X
  
  [29X[2XZeroMutable[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya  mutable  copy of the zero [10Xcmat[110X over the same field and with the
            same dimensions as [3Xm[103X[133X
  
  [33X[0;0Y[3Xm[103X must be a [10Xcmat[110X.[133X
  
  [1X5.3-11 OneSameMutability[101X
  
  [29X[2XOneSameMutability[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe identity [10Xcmat[110X over the same field and with the same dimensions
            as [3Xm[103X[133X
  
  [33X[0;0Y[3Xm[103X must be a square [10Xcmat[110X.[133X
  
  [1X5.3-12 OneMutable[101X
  
  [29X[2XOneMutable[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya  mutable  copy of the identity [10Xcmat[110X over the same field and with
            the same dimensions as [3Xm[103X[133X
  
  [33X[0;0Y[3Xm[103X must be a square [10Xcmat[110X.[133X
  
  [1X5.3-13 InverseMutable[101X
  
  [29X[2XInverseMutable[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe multiplicative inverse of [3Xm[103X[133X
  
  [33X[0;0YIf  the  [10Xcmat[110X is not square or not invertible then [10Xfail[110X is returned. Behaves
  exactly as expected.[133X
  
  [1X5.3-14 InverseSameMutability[101X
  
  [29X[2XInverseSameMutability[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe multiplicative inverse of [3Xm[103X[133X
  
  [33X[0;0YIf  the  [10Xcmat[110X is not square or not invertible then [10Xfail[110X is returned. Behaves
  exactly as expected.[133X
  
  [1X5.3-15 TransposedMat[101X
  
  [29X[2XTransposedMat[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe transpose of [3Xm[103X[133X
  
  [33X[0;0YBehaves exactly as expected.[133X
  
  [1X5.3-16 KroneckerProduct[101X
  
  [29X[2XKroneckerProduct[102X( [3Xm[103X, [3Xn[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe Kronecker product of [3Xm[103X and [3Xn[103X[133X
  
  [33X[0;0YBehaves exactly as expected.[133X
  
  
  [1X5.4 [33X[0;0YComparison of matrices and other information[133X[101X
  
  [1X5.4-1 =[101X
  
  [29X[2X=[102X( [3Xm[103X, [3Xn[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfalse[110X[133X
  
  [33X[0;0YReturns  [10Xtrue[110X  if the [10Xcmat[110Xs [3Xm[103X and [3Xn[103X are equal. The matrices must be over the
  same field and must have equal dimensions.[133X
  
  [1X5.4-2 LT[101X
  
  [29X[2XLT[102X( [3Xm[103X, [3Xn[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfalse[110X[133X
  
  [33X[0;0YReturns  [10Xtrue[110X if the [10Xcmat[110X [3Xm[103X is smaller than [3Xn[103X. The matrices must be over the
  same  field  and  must  have  equal  dimensions.  The  method implements the
  lexicographic  order  and uses [2XLT[102X for the ordering of vectors. Note that the
  operation [10XLT[110X is the same as [10X\<[110X.[133X
  
  [1X5.4-3 IsZero[101X
  
  [29X[2XIsZero[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfalse[110X[133X
  
  [33X[0;0YReturns  [10Xtrue[110X  if  the [10Xcmat[110X [3Xm[103X is equal to zero, meaning that all entries are
  equal to zero.[133X
  
  [1X5.4-4 IsOne[101X
  
  [29X[2XIsOne[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfalse[110X[133X
  
  [33X[0;0YReturns [10Xtrue[110X iff the [10Xcmat[110X [3Xm[103X is equal to the identity matrix.[133X
  
  [1X5.4-5 IsDiagonalMat[101X
  
  [29X[2XIsDiagonalMat[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfalse[110X[133X
  
  [33X[0;0YReturns [10Xtrue[110X iff the [10Xcmat[110X [3Xm[103X is a diagonal matrix.[133X
  
  [1X5.4-6 IsUpperTriangularMat[101X
  
  [29X[2XIsUpperTriangularMat[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfalse[110X[133X
  
  [33X[0;0YReturns [10Xtrue[110X iff the [10Xcmat[110X [3Xm[103X is an upper triangular matrix.[133X
  
  [1X5.4-7 IsLowerTriangularMat[101X
  
  [29X[2XIsLowerTriangularMat[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfalse[110X[133X
  
  [33X[0;0YReturns [10Xtrue[110X iff the [10Xcmat[110X [3Xm[103X is a lower triangular matrix.[133X
  
  [1X5.4-8 CVEC_HashFunctionForCMats[101X
  
  [29X[2XCVEC_HashFunctionForCMats[102X( [3Xm[103X, [3Xdata[103X ) [32X function
  [6XReturns:[106X  [33X[0;10Yan integer hash value[133X
  
  [33X[0;0YThis   is   a   hash   function  usable  for  the  [2XChooseHashFunction[102X  ([14Xorb:
  ChooseHashFunction[114X)  framework.  It  takes  as arguments a [10Xcmat[110X [3Xm[103X and a list
  [3Xdata[103X  of  length  [22X2[122X. The first entry of [3Xdata[103X is the length of the hash table
  used  and  the second entry is the number of bytes looked at in the [10Xcvec[110Xs in
  the matrices.[133X
  
  [1X5.4-9 ChooseHashFunction[101X
  
  [29X[2XChooseHashFunction[102X( [3Xm[103X, [3Xl[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya record with entries [10Xfunc[110X and [10Xdata[110X.[133X
  
  [33X[0;0YChooses  a hash function to be used for [10Xcmat[110Xs like [3Xm[103X (that is, over the same
  field  with the same number of columns) and for hash tables of length [3Xl[103X. The
  hash  function  itself  is  stored  in  the  [10Xfunc[110X component of the resulting
  record.  The  hash  function  has to be called with two arguments: the first
  must  be  a  matrix  like  [3Xm[103X  and  the  second must be the value of the [10Xdata[110X
  component of the resulting record.[133X
  
  
  [1X5.5 [33X[0;0YSlicing and submatrices[133X[101X
  
  [33X[0;0YAs  described  in Section [14X5.2[114X you can use the slicing operator [10X\{\}[110X for read
  and  write  access  of  a  subset of the rows of a [10Xcmat[110X. However, the double
  slicing  operator  is  not  supported. The reason for this is twofold: First
  there is a technical issue that the double slicing operator cannot easily be
  overloaded  in  the  [5XGAP[105X  system.  The second is, that very often the double
  slicing  operator  is  used  to copy a part of one matrix to another part of
  another  matrix using double slicing on both sides of an assignment. This is
  quite  inefficient  because  it  creates  an intermediate object, namely the
  submatrix which is extracted.[133X
  
  [33X[0;0YTherefore  we have chosen to support submatrix access through two operations
  [2XExtractSubMatrix[102X ([14X5.5-1[114X) and [2XCopySubMatrix[102X ([14X5.5-2[114X) described below.[133X
  
  [1X5.5-1 ExtractSubMatrix[101X
  
  [29X[2XExtractSubMatrix[102X( [3Xm[103X, [3Xrows[103X, [3Xcols[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10Ya submatrix of [3Xm[103X[133X
  
  [33X[0;0YThis operation extracts the submatrix of the matrix [3Xm[103X consisting of the rows
  described  by  the integer list (or range) [3Xrows[103X and of the columns described
  by  the  integer  list (or range) [3Xcols[103X. This is thus equivalent to the usage
  [3Xm[103X[10X{[110X[3Xrows[103X[10X}{[110X[3Xcols[103X[10X}[110X. Note that the latter does not work for [10Xcmat[110Xs, whereas a quite
  efficient method for [2XExtractSubMatrix[102X is available for [10Xcmat[110Xs.[133X
  
  [1X5.5-2 CopySubMatrix[101X
  
  [29X[2XCopySubMatrix[102X( [3Xsrc[103X, [3Xdst[103X, [3Xsrows[103X, [3Xdrows[103X, [3Xscols[103X, [3Xdcols[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10Ynothing[133X
  
  [33X[0;0YThis  operation  extracts  the submatrix of the matrix [3Xsrc[103X consisting of the
  rows  described  by  the  integer  list  (or range) [3Xsrows[103X and of the columns
  described  by  the  integer  list  (or  range)  [3Xscols[103X and copies it into the
  submatrix of [3Xdst[103X described by the integer lists (or ranges) [3Xdrows[103X and [3Xdcols[103X.
  No  intermediate  object  is  created.  This is thus equivalent to the usage
  [3Xdst[103X[10X{[110X[3Xdrows[103X[10X}{[110X[3Xdcols[103X[10X}  :=  [110X[3Xsrc[103X[10X{[110X[3Xsrows[103X[10X}{[110X[3Xscols[103X[10X}[110X. Note that the latter does not work
  for  [10Xcmat[110Xs,  whereas a quite efficient method for [2XCopySubMatrix[102X is available
  for [10Xcmat[110Xs.[133X
  
  
  [1X5.6 [33X[0;0YInformation about matrices[133X[101X
  
  [1X5.6-1 BaseField[101X
  
  [29X[2XBaseField[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe base field of [3Xm[103X[133X
  
  [33X[0;0YFor  a  [10Xcmat[110X [3Xm[103X this returns the [5XGAP[105X object [10XGF(p,d)[110X corresponding to the base
  field of [3Xm[103X. Note that this is a relatively fast lookup.[133X
  
  [1X5.6-2 Characteristic[101X
  
  [29X[2XCharacteristic[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe characteristic of the base field of [3Xm[103X[133X
  
  [33X[0;0YReturns the characteristic of the base field of [3Xm[103X (see [2XBaseField[102X ([14X5.6-1[114X)).[133X
  
  [1X5.6-3 DegreeFFE[101X
  
  [29X[2XDegreeFFE[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe degree of the base field of [3Xm[103X over its prime field[133X
  
  [33X[0;0YReturns  the  degree  of  the  base  field  of  [3Xm[103X  over its prime field (see
  [2XBaseField[102X ([14X5.6-1[114X)).[133X
  
  [1X5.6-4 DefaultField[101X
  
  [29X[2XDefaultField[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe base field of [3Xm[103X[133X
  
  [33X[0;0YFor  a  [10Xcmat[110X [3Xm[103X this returns the [5XGAP[105X object [10XGF(p,d)[110X corresponding to the base
  field of [3Xm[103X. Note that this is a relatively fast lookup.[133X
  
  
  [1X5.7 [33X[0;0YInput and output[133X[101X
  
  [1X5.7-1 CVEC_WriteMat[101X
  
  [29X[2XCVEC_WriteMat[102X( [3Xf[103X, [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfail[110X[133X
  
  [33X[0;0Y[3Xf[103X  must be a file object from the [5XIO[105X package (see [2XIsFile[102X ([14XIO: IsFile[114X)) and [3Xm[103X
  must  be a [10Xcmat[110X. The matrix [3Xm[103X is written to the file [3Xf[103X. Note that the format
  (see  Section  [14X3.4[114X)  is  platform  independent,  such  that  matrices can be
  exchanged  between  different  architectures.  The  result  is  [10Xtrue[110X or [10Xfail[110X
  depending on whether everything worked or an error occurred respectively.[133X
  
  [1X5.7-2 CVEC_WriteMatToFile[101X
  
  [29X[2XCVEC_WriteMatToFile[102X( [3Xfn[103X, [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfail[110X[133X
  
  [33X[0;0Y[3Xfn[103X  must be a string object containing a file name and [3Xm[103X must be a [10Xcmat[110X. The
  matrix [3Xm[103X is written to the file with name [3Xfn[103X on the local storage. Note that
  the format (see Section [14X3.4[114X) is platform independent, such that matrices can
  be  exchanged  between  different  architectures. The result is [10Xtrue[110X or [10Xfail[110X
  depending on whether everything worked or an error occurred respectively.[133X
  
  [1X5.7-3 CVEC_WriteMatsToFile[101X
  
  [29X[2XCVEC_WriteMatsToFile[102X( [3Xfnpref[103X, [3Xl[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Y[10Xtrue[110X or [10Xfail[110X[133X
  
  [33X[0;0Y[3Xfnpref[103X must be a string object containing a file name prefix and [3Xm[103X must be a
  list  of  [10Xcmat[110Xs.  The  matrices  in  [3Xl[103X  are  written to the files with names
  determined by using the string [3Xfnpref[103X and appending the natural numbers from
  [22X1[122X to the length of [3Xl[103X on the local storage. Note that the format (see Section
  [14X3.4[114X)  is  platform  independent, such that matrices can be exchanged between
  different  architectures.  The  result  is [10Xtrue[110X or [10Xfail[110X depending on whether
  everything worked or an error occurred respectively.[133X
  
  [1X5.7-4 CVEC_ReadMat[101X
  
  [29X[2XCVEC_ReadMat[102X( [3Xf[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya [10Xcmat[110X or [10Xfail[110X[133X
  
  [33X[0;0Y[3Xf[103X  must  be  a  file object from the [5XIO[105X package (see [2XIsFile[102X ([14XIO: IsFile[114X)). A
  matrix  is  read  from the file [3Xf[103X. Note that the format (see Section [14X3.4[114X) is
  platform  independent, such that matrices can be exchanged between different
  architectures. The result is [10Xfail[110X if an error occurred.[133X
  
  [1X5.7-5 CVEC_ReadMatFromFile[101X
  
  [29X[2XCVEC_ReadMatFromFile[102X( [3Xfn[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya [10Xcmat[110X or [10Xfail[110X[133X
  
  [33X[0;0Y[3Xfn[103X must be a string object containing a file name. A matrix is read from the
  file  with  name  [3Xfn[103X on the local storage. Note that the format (see Section
  [14X3.4[114X)  is  platform  independent, such that matrices can be exchanged between
  different architectures. The result is [10Xfail[110X if an error occurred.[133X
  
  [1X5.7-6 CVEC_ReadMatsFromFile[101X
  
  [29X[2XCVEC_ReadMatsFromFile[102X( [3Xfnpref[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya list of [10Xcmat[110Xs or [10Xfail[110X[133X
  
  [33X[0;0Y[3Xfnpref[103X  must  be  a  string  object containing a file name prefix. A list of
  matrices  is  read  from the files with names determined by using the string
  [3Xfnpref[103X  and  appending the natural numbers from [22X1[122X on from the local storage.
  The  number  of  matrices read is determined by the highest number such that
  the  corresponding  filename  exists in the filesystem. Note that the format
  (see  Section  [14X3.4[114X)  is  platform  independent,  such  that  matrices can be
  exchanged  between  different  architectures. The result is [10Xfail[110X if an error
  occurred.[133X
  
  
  [1X5.8 [33X[0;0YGrease[133X[101X
  
  [33X[0;0YThe basic idea behind the [21Xgrease[121X technique is that over a finite field there
  are only finitely many linear combinations of a fixed list of vectors. Thus,
  many  operations  including  matrix  multiplication  can  be  speeded  up by
  precomputing  all  possible linear combinations and then just looking up the
  right one. For the case of matrix multiplication this can for example gain a
  factor  of about [22X4[122X over the field with [22X2[122X elements using [21Xgrease level[22X8[122X[121X, which
  means that for blocks of [22X8[122X rows all linear combinations are precomputed.[133X
  
  [33X[0;0YThe  [5Xcvec[105X  uses  grease  whenever  appropriate automatically for example for
  matrix  multiplication.  However,  occasionally  the  user  has  to  take  a
  conscious  decision,  which  matrices to grease, because this of course uses
  more memory.[133X
  
  [33X[0;0YA  [10Xcmat[110X can be [21Xpre-greased[121X with level [22Xl[122X, which means that it is chopped into
  chunks  of  [22Xl[122X  rows and for each such chunk all possible linear combinations
  are  precomputed  and  stored.  This  increases the memory used to store the
  matrix  by  a  factor of [22Xq^l[122X if the base field of the matrix has [22Xq[122X elements.
  However,  operations  like  vector  matrix  multiplication and matrix matrix
  multiplication  (here  the  right  hand  side  matrix  must be greased!) are
  speeded  up.  As  a  rule  of thumb the factor one can hope for is about [22Xl ⋅
  (q-1)/q[122X.  Note  that for big matrices matrix multiplication does greasing on
  the  fly  anyway  and  therefore  one  cannot  hope for such a big factor by
  pre-greasing.[133X
  
  [1X5.8-1 GreaseMat[101X
  
  [29X[2XGreaseMat[102X( [3Xm[103X, [3Xl[103X ) [32X operation
  [29X[2XGreaseMat[102X( [3Xm[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10Ynothing[133X
  
  [33X[0;0Y[3Xm[103X  must  be  a [10Xcmat[110X. It is pregreased with level [3Xl[103X. Without the argument [3Xl[103X a
  grease  level depending of the field size is chosen automatically. Note that
  the matrix will need much more memory when pregreased.[133X
  
  [1X5.8-2 UnGreaseMat[101X
  
  [29X[2XUnGreaseMat[102X( [3Xm[103X ) [32X operation
  [6XReturns:[106X  [33X[0;10Ynothing[133X
  
  [33X[0;0Y[3Xm[103X must be a [10Xcmat[110X. The pregreased information is deleted. This can save a lot
  of memory.[133X
  
  
  [1X5.9 [33X[0;0YEverything else[133X[101X
  
  [1X5.9-1 Randomize[101X
  
  [29X[2XRandomize[102X( [3Xm[103X ) [32X method
  [29X[2XRandomize[102X( [3Xm[103X, [3Xrs[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ythe matrix [3Xm[103X[133X
  
  [33X[0;0Y[3Xm[103X must be a [10Xcmat[110X and [3Xrs[103X must be a random source object if given. This method
  changes  the  matrix  [3Xm[103X in place by (pseudo) random values in the field over
  which  the  matrix  lives.  If  a  random source is given, the pseudo random
  numbers  used are taken from this source, otherwise the global random source
  in the [5XGAP[105X library is taken.[133X
  
  [1X5.9-2 OverviewMat[101X
  
  [29X[2XOverviewMat[102X( [3Xm[103X ) [32X function
  [6XReturns:[106X  [33X[0;10Ynothing[133X
  
  [33X[0;0YAn  ASCII  art  overview  over the [10Xcmat[110X [3Xm[103X is printed. Stars indicate nonzero
  blocks in the matrix and dots zero blocks.[133X
  
  [1X5.9-3 Unpack[101X
  
  [29X[2XUnpack[102X( [3Xm[103X ) [32X method
  [6XReturns:[106X  [33X[0;10Ya list of lists of finite field elements[133X
  
  [33X[0;0YThis  operation unpacks a [10Xcmat[110X [3Xm[103X. A new plain list of plain lists containing
  the corresponding numbers as [5XGAP[105X finite field elements. Note that the matrix
  [3Xm[103X remains unchanged.[133X
  
