Somewhere in the E.U., le 11/08/2005 Bonjour Peeking back after vacations are over... In article <BAY104-DAV130A4664B11F6CDE9DB931BFD20@phx.gbl>, Daryle Walker <darylew@hotmail.com> wrote:
This is for the "ll" function defined for quaternions and octonions. The function returns the 1-norm of its argument. Does anyone know what the "ll" name stands for? I finally figured out that "sup" (the infinity-norm) most likely stands for "supremum". (BTW, "abs" is the 2-norm. The "norm" function isn't actually in this system, despite the name!)
it is actually the L1 (ell-one) norm (sum of the norm of the components, the lp norm would be the sum of the p-th power of the norm of the components, and the l-infinite norm is just the supremum of the norm of the components). This was to be consistent with the usual mathematical terminology (lower-case "l" for the norm of sequence spaces, upper-case "l" for other measured spaces, though in this case we only have a quadruple or an octuple). I agree the resemblance between the "l" and the "1" is quite unfortunate. I have no special love for that notation, but fear that changing it now would be more hassle than what it's worth. At the very least, I'll add a note to the documentation after the 1.33 release. Merci Hubert Holin