mpf exponent range

[Torbjorn Granlund]

We recently improved the logarithm calculations needed for input and
output conversion of mpf numbers.  Before this fix, things started to
work unreliably for exponents (in some base) of over about 2^50.

Now, input and output work for numbers up to about 2^(2^63-1) (for
64-bit machines).  During computations, much larger numbers, up to
(2^64)^(2^63-1) are expected to work.

I realise mpf isn't terribly much used today, given the existence of the
superior mpfr functions.  Do people on this list have any opinions about
the exponent range, of mpf, in particular, if we should make input and
output work for the entire allowed number range?  Or is this irrelevant?

It is not a trivial fix.  The required changes will be to allow
multi-word exponents (for bases < 2^64).

-- 
Torbjörn