ZTREXC(3)
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
SYNOPSIS
 SUBROUTINE ZTREXC(

COMPQ, N, T, LDT, Q, LDQ, IFST, ILST, INFO )

CHARACTER
COMPQ

INTEGER
IFST, ILST, INFO, LDQ, LDT, N

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
 COMPQ (input) CHARACTER*1

= 'V': update the matrix Q of Schur vectors;
= 'N': do not update Q.
 N (input) INTEGER

The order of the matrix T. N >= 0.
 T (input/output) COMPLEX*16 array, dimension (LDT,N)

On entry, the upper triangular matrix T.
On exit, the reordered upper triangular matrix.
 LDT (input) INTEGER

The leading dimension of the array T. LDT >= max(1,N).
 Q (input/output) 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.
 LDQ (input) INTEGER

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

ILST (input) 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.
 INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value