gmp 4.1 documentation improvement suggestions

[Paul Zimmermann]

   Well, if you rewrite it like this, then there is still no mention of the
   fact that the precision stored in a variable may be very different from
   the logically defined precision of the result (e.g. when two
   low-precision variables are multiplied and the result variable has high
   precision set in it), i.e. mpfr does not precision tracking. I'd say
   that this point is important for anyone who wants to develop
   floating-point applications using mpfr.

You are right. Then I propose to add this after the "precision" paragraph:

@cindex Accuracy
MPFR does not keep track of the accuracy of a computation. This is left
to the user or to a higher layer.
As a consequence, if two variables are used to store only a few significant
bits, and their product is stored in a variable with large
precision, then MPFR will still compute the result with full precision.

Paul

PS: MPFI does not exactly answer this problem, since it will still compute
with a large precision in that case.