Description: Dirac bra-ket associative law
( | A >. <. B | ) | C >. = | A >. ( <. B | C >. ) , i.e., the
juxtaposition of an outer product with a ket equals a bra juxtaposed
with an inner product. Since <. B | C >. is a complex number, it is
the first argument in the inner product .h that it is mapped to,
although in Dirac notation it is placed after the ket. (Contributed by NM, 15-May-2006)(New usage is discouraged.)