*> \brief \b DLANST returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real symmetric tridiagonal matrix.
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at 
*            http://www.netlib.org/lapack/explore-html/ 
*
*> \htmlonly
*> Download DLANST + dependencies 
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlanst.f"> 
*> [TGZ]</a> 
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlanst.f"> 
*> [ZIP]</a> 
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlanst.f"> 
*> [TXT]</a>
*> \endhtmlonly 
*
*  Definition:
*  ===========
*
*       DOUBLE PRECISION FUNCTION DLANST( NORM, N, D, E )
* 
*       .. Scalar Arguments ..
*       CHARACTER          NORM
*       INTEGER            N
*       ..
*       .. Array Arguments ..
*       DOUBLE PRECISION   D( * ), E( * )
*       ..
*  
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> DLANST  returns the value of the one norm,  or the Frobenius norm, or
*> the  infinity norm,  or the  element of  largest absolute value  of a
*> real symmetric tridiagonal matrix A.
*> \endverbatim
*>
*> \return DLANST
*> \verbatim
*>
*>    DLANST = ( max(abs(A(i,j))), NORM = 'M' or 'm'
*>             (
*>             ( norm1(A),         NORM = '1', 'O' or 'o'
*>             (
*>             ( normI(A),         NORM = 'I' or 'i'
*>             (
*>             ( normF(A),         NORM = 'F', 'f', 'E' or 'e'
*>
*> where  norm1  denotes the  one norm of a matrix (maximum column sum),
*> normI  denotes the  infinity norm  of a matrix  (maximum row sum) and
*> normF  denotes the  Frobenius norm of a matrix (square root of sum of
*> squares).  Note that  max(abs(A(i,j)))  is not a consistent matrix norm.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] NORM
*> \verbatim
*>          NORM is CHARACTER*1
*>          Specifies the value to be returned in DLANST as described
*>          above.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>          The order of the matrix A.  N >= 0.  When N = 0, DLANST is
*>          set to zero.
*> \endverbatim
*>
*> \param[in] D
*> \verbatim
*>          D is DOUBLE PRECISION array, dimension (N)
*>          The diagonal elements of A.
*> \endverbatim
*>
*> \param[in] E
*> \verbatim
*>          E is DOUBLE PRECISION array, dimension (N-1)
*>          The (n-1) sub-diagonal or super-diagonal elements of A.
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee 
*> \author Univ. of California Berkeley 
*> \author Univ. of Colorado Denver 
*> \author NAG Ltd. 
*
*> \date September 2012
*
*> \ingroup auxOTHERauxiliary
*
*  =====================================================================
      DOUBLE PRECISION FUNCTION GAL_DLANST(NORM,N,D,E)
*
*  -- LAPACK auxiliary routine (version 3.4.2) --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     September 2012
*
*     .. Scalar Arguments ..
      CHARACTERNORM
      INTEGER N
*     ..
*     .. Array Arguments ..
      DOUBLE PRECISION D(*),E(*)
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      DOUBLE PRECISION ONE,ZERO
      PARAMETER (ONE=1.0D+0,ZERO=0.0D+0)
*     ..
*     .. Local Scalars ..
      INTEGER I
      DOUBLE PRECISION ANORM,SCALE,SUM
*     ..
*     .. External Functions ..
      LOGICAL GAL_LSAME,GAL_DISNAN
      EXTERNAL GAL_LSAME,GAL_DISNAN
*     ..
*     .. External Subroutines ..
      EXTERNAL GAL_DLASSQ
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC ABS,SQRT
*     ..
*     .. Executable Statements ..
*
      IF(N.LE.0)THEN
      ANORM=ZERO
      ELSE IF(GAL_LSAME(NORM,'M'))THEN
*
*        Find max(abs(A(i,j))).
*
      ANORM=ABS(D(N))
      DO 10I=1,N-1
      SUM=ABS(D(I))
      IF(ANORM.LT.SUM.OR.GAL_DISNAN(SUM))ANORM=SUM
      SUM=ABS(E(I))
      IF(ANORM.LT.SUM.OR.GAL_DISNAN(SUM))ANORM=SUM
   10 CONTINUE
      ELSE IF(GAL_LSAME(NORM,'O').OR.NORM.EQ.'1'.OR.
     $GAL_LSAME(NORM,'I'))THEN
*
*        Find norm1(A).
*
      IF(N.EQ.1)THEN
      ANORM=ABS(D(1))
      ELSE 
      ANORM=ABS(D(1))+ABS(E(1))
      SUM=ABS(E(N-1))+ABS(D(N))
      IF(ANORM.LT.SUM.OR.GAL_DISNAN(SUM))ANORM=SUM
      DO 20I=2,N-1
      SUM=ABS(D(I))+ABS(E(I))+ABS(E(I-1))
      IF(ANORM.LT.SUM.OR.GAL_DISNAN(SUM))ANORM=SUM
   20 CONTINUE
      END IF
      ELSE IF((GAL_LSAME(NORM,'F')).OR.(GAL_LSAME(NORM,'E')))THEN
*
*        Find normF(A).
*
      SCALE=ZERO
      SUM=ONE
      IF(N.GT.1)THEN
      CALL GAL_DLASSQ(N-1,E,1,SCALE,SUM)
      SUM=2*SUM
      END IF
      CALL GAL_DLASSQ(N,D,1,SCALE,SUM)
      ANORM=SCALE*SQRT(SUM)
      END IF
*
      GAL_DLANST=ANORM
      RETURN
*
*     End of DLANST
*
      END 
