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)abbrev package NCEP NumericComplexEigenPackage
++ Author: P. Gianni
++ Date Created: Summer 1990
++ Date Last Updated: Spring 1991
++ Description:
++ This package computes explicitly eigenvalues and eigenvectors of
++ matrices with entries over the complex rational numbers.
++ The results are expressed either as complex floating numbers or as
++ complex rational numbers depending on the type of the precision parameter.

NumericComplexEigenPackage(Par) : SIG == CODE where
  Par : Join(Field,OrderedRing)   -- Float or RationalNumber

  SE    ==> Symbol()
  RN    ==> Fraction Integer
  I     ==> Integer
  NF    ==> Float
  CF    ==> Complex Float
  GRN   ==> Complex RN
  GI    ==> Complex Integer
  PI    ==> PositiveInteger
  NNI   ==> NonNegativeInteger
  MRN   ==> Matrix RN
  MCF        ==> Matrix CF
  MGRN       ==> Matrix GRN
  MCPar      ==> Matrix Complex Par
  SUPGRN     ==> SparseUnivariatePolynomial GRN
  outForm    ==> Record(outval:Complex Par,outmult:Integer,outvect:List MCPar)

  SIG ==> with

    characteristicPolynomial : MGRN -> Polynomial GRN
      ++ characteristicPolynomial(m) returns the characteristic polynomial
      ++ of the matrix m expressed as polynomial
      ++ over complex rationals with a new symbol as variable.
      -- while the function in EigenPackage returns Fraction P GRN.

    characteristicPolynomial : (MGRN,SE) -> Polynomial GRN
      ++ characteristicPolynomial(m,x) returns the characteristic polynomial
      ++ of the matrix m expressed as polynomial
      ++ over Complex Rationals with variable x.
      -- while the function in EigenPackage returns Fraction P GRN.

    complexEigenvalues : (MGRN,Par) -> List Complex Par
      ++ complexEigenvalues(m,eps) computes the eigenvalues of the matrix
      ++ m to precision eps. The eigenvalues are expressed as complex 
      ++ floats or complex rational numbers depending on the type of 
      ++ eps (float or rational).

    complexEigenvectors : (MGRN,Par) -> List(outForm)
      ++ complexEigenvectors(m,eps)  returns a list of
      ++ records each one containing
      ++ a complex eigenvalue, its algebraic multiplicity, and a list of
      ++ associated eigenvectors. All these results
      ++ are computed to precision eps and are expressed as complex floats
      ++ or complex rational numbers depending on the type of 
      ++ eps (float or rational).

  CODE ==> add

     import InnerNumericEigenPackage(GRN,Complex Par,Par)

     characteristicPolynomial(m:MGRN) : Polynomial GRN  ==
       x:SE:=new()$SE
       multivariate(charpol m, x)

            ----  characteristic polynomial of a matrix A ----
     characteristicPolynomial(A:MGRN,x:SE):Polynomial GRN ==
       multivariate(charpol A, x)

     complexEigenvalues(m:MGRN,eps:Par) : List Complex Par  ==
       solve1(charpol m, eps)

     complexEigenvectors(m:MGRN,eps:Par) :List outForm ==
       innerEigenvectors(m,eps,factor$ComplexFactorization(RN,SUPGRN))