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ztrexc examples
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Man Page Details
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 Online html documentation available at 
            http://www.netlib.org/lapack/explore-html/ 

 Definition:
 ===========

       SUBROUTINE ZTREXC( COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, INFO )
 
       .. Scalar Arguments ..
       CHARACTER          COMPQ
       INTEGER            IFST, ILST, INFO, LDQ, LDT, N
       ..
       .. Array Arguments ..
       COMPLEX*16         Q( LDQ, * ), T( LDT, * )
       ..
  

 Purpose:
 =============

 ZTREXC reorders the Schur factorization of a complex matrix
 A = Q*T*Q**H, so that the diagonal element of T with row index IFST
 is moved to row ILST.

 The Schur form T is reordered by a unitary similarity transformation
 Z**H*T*Z, and optionally the matrix Q of Schur vectors is updated by
 postmultplying it with Z.

 Arguments:
 ==========

  [in] COMPQ

          COMPQ is CHARACTER*1
          = 'V':  update the matrix Q of Schur vectors;
          = 'N':  do not update Q.

  [in] N

          N is INTEGER
          The order of the matrix T. N >= 0.

  [in,out] T

          T is COMPLEX*16 array, dimension (LDT,N)
          On entry, the upper triangular matrix T.
          On exit, the reordered upper triangular matrix.

  [in] LDT

          LDT is INTEGER
          The leading dimension of the array T. LDT >= max(1,N).

  [in,out] Q

          Q is COMPLEX*16 array, dimension (LDQ,N)
          On entry, if COMPQ = 'V', the matrix Q of Schur vectors.
          On exit, if COMPQ = 'V', Q has been postmultiplied by the
          unitary transformation matrix Z which reorders T.
          If COMPQ = 'N', Q is not referenced.

  [in] LDQ

          LDQ is INTEGER
          The leading dimension of the array Q.  LDQ >= max(1,N).

  [in] IFST

          IFST is INTEGER

  [in] ILST

          ILST is INTEGER

          Specify the reordering of the diagonal elements of T:
          The element with row index IFST is moved to row ILST by a
          sequence of transpositions between adjacent elements.
          1 <= IFST <= N; 1 <= ILST <= N.

  [out] INFO

          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value

 Authors:
 ========

  Univ. of Tennessee 
  Univ. of California Berkeley 
  Univ. of Colorado Denver 
  NAG Ltd. 

 November 2011

