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NAME
     slantb - return the value of the one norm, or the  Frobenius
     norm,  or the infinity norm, or the element of largest abso-
     lute value of an n by n triangular band matrix A, with ( k +
     1 ) diagonals

SYNOPSIS
     REAL FUNCTION SLANTB( NORM, UPLO, DIAG, N, K, AB, LDAB, WORK
               )

     CHARACTER DIAG, NORM, UPLO

     INTEGER K, LDAB, N

     REAL AB( LDAB, * ), WORK( * )



     #include <sunperf.h>

     double slantb(char norm, char uplo, char diag, int n, int k,
               float *sab, int ldab) ;

PURPOSE
     SLANTB  returns the value of the one norm,  or the Frobenius
     norm,  or  the   infinity  norm,  or the element of  largest
     absolute value  of an n by n triangular band matrix A,  with
     ( k + 1 ) diagonals.


DESCRIPTION
     SLANTB returns the value

        SLANTB = ( 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  matrix norm.


ARGUMENTS
     NORM      (input) CHARACTER*1
               Specifies the value to be returned  in  SLANTB  as
               described above.

     UPLO      (input) CHARACTER*1
               Specifies whether the matrix A is upper  or  lower
               triangular.  = 'U':  Upper triangular
               = 'L':  Lower triangular

     DIAG      (input) CHARACTER*1
               Specifies whether or not the matrix A is unit tri-
               angular.  = 'N':  Non-unit triangular
               = 'U':  Unit triangular

     N         (input) INTEGER
               The order of the matrix A.  N >= 0.  When N  =  0,
               SLANTB is set to zero.

     K         (input) INTEGER
               The number of super-diagonals of the matrix  A  if
               UPLO  = 'U', or the number of sub-diagonals of the
               matrix A if UPLO = 'L'.  K >= 0.

     AB        (input) REAL array, dimension (LDAB,N)
               The upper  or  lower  triangular  band  matrix  A,
               stored  in  the  first  k+1  rows of AB.  The j-th
               column of A is stored in the j-th  column  of  the
               array AB as follows:  if UPLO = 'U', AB(k+1+i-j,j)
               = A(i,j) for  max(1,j-k)<=i<=j;  if  UPLO  =  'L',
               AB(1+i-j,j)   = A(i,j) for j<=i<=min(n,j+k).  Note
               that when DIAG = 'U', the elements of the array AB
               corresponding  to  the  diagonal  elements  of the
               matrix A are not referenced, but are assumed to be
               one.

     LDAB      (input) INTEGER
               The leading dimension of the array  AB.   LDAB  >=
               K+1.

     WORK      (workspace) REAL array, dimension (LWORK),
               where LWORK >= N when NORM = 'I'; otherwise,  WORK
               is not referenced.

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