[Qtfm-announce] QTFM version 3.2

[Release a. a. u. <qtf...@li...>]

A new release of the Quaternion Toolbox for Matlab (QTFM) has been 
posted on Sourceforge.

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                 Quaternion toolbox for Matlab
                 http://qtfm.sourceforge.net/
        Mailing list: qtf...@li...
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Copyright © 2005-2022 Stephen J. Sangwine & Nicolas Le Bihan
Email: san...@us...
        nic...@gi...
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                      Release Notes

Version 3.2 8 September 2022

The function DISPLAY has been removed from the toolbox. According to
current Mathworks advice (Code Analyzer) it should not be overloaded.
Removing it means that the built-in DISPLAY function is called when needed,
and this then calls the overloaded quaternion or octonion DISP function as
appropriate.

The functions ISDIVISOR and ISNILPOTENT now work for symbolic quaternions
and octonions.

A bug in the pivoting code in the LU decomposition has been fixed. The
candidate pivot values were wrongly taken from the diagonal below and
including A(j,j) rather than from the column below and including A(j,j).
Fixing this bug has resolved an issue in the test code, which manifested as
failures with complex octonion matrices, but could in fact have affected
any quaternion or octonion matrix. The bug came to light when working on
the Clifford Toolbox for MATLAB with algebras of large dimension (because
this increased the chance of a large out of tolerance error in the test
code). Since the LU code is common to this toolbox and the complex octonion
case was a known problem, it was possible to work out where the problem was
occurring.

The quaternion INV function has been modified to recover from Infs or NaNs
in intermediate results, by attempting to use adjoint matrices (isomorphic
real or complex matrices). If this works, a correct result will now be
returned, otherwise the result will, as before, still contain Infs or Nans.

A test case has been added to the test code.