- Report the problem in the Linux ldexp manual page.  The second and
  third calls in the Synopsis should be to ldexpf and ldexpl.

- [,] indexing

- group generics: "Arith" (partly done),
  but also "Compare", "Math" etc;
  see ?Math  and the examples in ?SetGeneric

- methods for rbind and cbind where they make sense

- consider moving alloc3Darray from ./src/Mutils.c to
  $(RSRC)/src/base/array.c

- data/ : names 'mm' and even more 'y' are  ``too short''.
	If we really want to keep them, don't use "LazyData"
	(such that one needs  data(*) explicitly);
	But MM would rather want something like  ex.mm and ex.y

- "factors" maybe should move up to "Matrix"

-------

We have a (at least one) basic problem :
   Currently the show() method fail sometime after coercion:
   e.g. 'sy' show()s wrongly, even though it "str()" fine :

      (po <- crossprod(Matrix(0:3, 2))) # ok
      (ge <- as(po, "dgeMatrix")) # ok
      (sy <- as(po, "dsyMatrix")) # BAD
      str(sy) # looks fine

  or
      example(expand) # -> ex$L and ex$U look bad, however
      as(ex$L, "dgeMatrix") # `works'

  {Of course, we don't need a workaround but must understand
   and solve the problem}

---

- implement (more) methods for supporting "packed" (symmetric / triangular)
  matrices; particularly something like pack() and unpack().

- implement diagonal Matrix class  "ddiMatrix" etc
  using constructor function Diagonal() or Diag().