# ?lanst/?lanht

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 or complex Hermitian tridiagonal matrix.

## Syntax

val = slanst( norm, n, d, e )

val = dlanst( norm, n, d, e )

val = clanht( norm, n, d, e )

val = zlanht( norm, n, d, e )

## Description

The functions ?lanst/?lanht return 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 or a complex Hermitian tridiagonal matrix A.

## Input Parameters

norm

  CHARACTER*1. Specifies the vaule to be returned by the routine:

  = 'M' or 'm': `val = max(abs(Aij))`, largest absolute value of the matrix A.

  = '1' or 'O' or 'o': `val = norm1(A)`, 1-norm of the matrix A (maximum column sum),

  = 'I' or 'i': `val = normI(A)`, infinity norm of the matrix A (maximum row sum),

  = 'F', 'f', 'E' or 'e': `val = normF(A)`, Frobenius norm of the matrix A (square root of sum of squares).

n

  INTEGER. The order of the matrix A.

  `n ≥ 0`. When `n = 0`, ?lanst/?lanht is set to zero.

d

  REAL for slanst/clanht

  DOUBLE PRECISION for dlanst/zlanht

  Array, DIMENSION (n). The diagonal elements of A.

e

  REAL for slanst

  DOUBLE PRECISION for dlanst

  COMPLEX for clanht

  COMPLEX*16 for zlanht

  Array, DIMENSION (n-1).

  The (n-1) sub-diagonal or super-diagonal elements of A.

## Output Parameters

val

  REAL for slanst/clanht

  DOUBLE PRECISION for dlanst/zlanht

  Value returned by the function.

Parent topic: Auxiliary Routines