text: /* ../netlib/dlanst.f -- translated by f2c (version 20100827). You must link the resulting object file with libf2c: on Microsoft Windows system, link with libf2c.lib;
   on Linux or Unix systems, link with .../path/to/libf2c.a -lm or, if you install libf2c.a in a standard place, with -lf2c -lm -- in that order, at the end of the command line, as in cc *.o -lf2c -lm Source for libf2c is in /netlib/f2c/libf2c.zip, e.g., http://www.netlib.org/f2c/libf2c.zip */
  #include "FLA_f2c.h" /* Table of constant values */
  static integer c__1 = 1;
  /* > \brief \b DLANST returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the ele ment 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(f2c_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(f2c_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 */
  /* ===================================================================== */
  doublereal dlanst_(char *norm, integer *n, doublereal *d__, doublereal *e)
  {
      /* System generated locals */
      integer i__1;
      doublereal ret_val, d__1, d__2, d__3;
      /* Builtin functions */
      double sqrt(doublereal);
      /* Local variables */
      integer i__;
      doublereal sum, scale;
      extern logical lsame_(char *, char *);
      doublereal anorm;
      extern logical disnan_(doublereal *);
      extern /* Subroutine */
      int dlassq_(integer *, doublereal *, integer *, doublereal *, doublereal *);
      /* -- 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 .. */
      /* .. */
      /* .. Array Arguments .. */
      /* .. */
      /* ===================================================================== */
      /* .. Parameters .. */
      /* .. */
      /* .. Local Scalars .. */
      /* .. */
      /* .. External Functions .. */
      /* .. */
      /* .. External Subroutines .. */
      /* .. */
      /* .. Intrinsic Functions .. */
      /* .. */
      /* .. Executable Statements .. */
      /* Parameter adjustments */
      --e;
      --d__;
      /* Function Body */
      if (*n <= 0)
      {
          anorm = 0.;
      }
      else if (lsame_(norm, "M"))
      {
          /* Find max(f2c_abs(A(i,j))). */
          anorm = (d__1 = d__[*n], f2c_abs(d__1));
          i__1 = *n - 1;
          for (i__ = 1;
                  i__ <= i__1;
                  ++i__)
          {
              sum = (d__1 = d__[i__], f2c_abs(d__1));
              if (anorm < sum || disnan_(&sum))
              {
                  anorm = sum;
              }
              sum = (d__1 = e[i__], f2c_abs(d__1));
              if (anorm < sum || disnan_(&sum))
              {
                  anorm = sum;
              }
              /* L10: */
          }
      }
      else if (lsame_(norm, "O") || *(unsigned char *) norm == '1' || lsame_(norm, "I"))
      {
          /* Find norm1(A). */
          if (*n == 1)
          {
              anorm = f2c_abs(d__[1]);
          }
          else
          {
              anorm = f2c_abs(d__[1]) + f2c_abs(e[1]);
              sum = (d__1 = e[*n - 1], f2c_abs(d__1)) + (d__2 = d__[*n], f2c_abs(d__2));
              if (anorm < sum || disnan_(&sum))
              {
                  anorm = sum;
              }
              i__1 = *n - 1;
              for (i__ = 2;
                      i__ <= i__1;
                      ++i__)
              {
                  sum = (d__1 = d__[i__], f2c_abs(d__1)) + (d__2 = e[i__], f2c_abs(d__2) ) + (d__3 = e[i__ - 1], f2c_abs(d__3));
                  if (anorm < sum || disnan_(&sum))
                  {
                      anorm = sum;
                  }
                  /* L20: */
              }
          }
      }
      else if (lsame_(norm, "F") || lsame_(norm, "E"))
      {
          /* Find normF(A). */
          scale = 0.;
          sum = 1.;
          if (*n > 1)
          {
              i__1 = *n - 1;
              dlassq_(&i__1, &e[1], &c__1, &scale, &sum);
              sum *= 2;
          }
          dlassq_(n, &d__[1], &c__1, &scale, &sum);
          anorm = scale * sqrt(sum);
      }
      ret_val = anorm;
      return ret_val;
      /* End of DLANST */
  }
  /* dlanst_ */
  