Add MPFR support to ForeignFunctions package

[d-torrance]

For example:

i1 : needsPackage "ForeignFunctions";

i2 : mpfrAdd = foreignFunction("mpfr_add", void, {mpfrT, mpfrT, mpfrT, int})

o2 = mpfr_add

o2 : ForeignFunction

i3 : x = mpfrT 0p100

o3 = 0

o3 : ForeignObject of type mpfr_t

i4 : mpfrAdd(x, numeric(100, pi), exp 1p100, 0)

i5 : x

o5 = 5.85987448204883847382293085463

o5 : ForeignObject of type mpfr_t

i6 : value oo

o6 = 5.85987448204883847382293085463

o6 : RR (of precision 100)

[mahrud]

I'm a bit confused. Ideally one shouldn't need any changes to the interpreter/engine to connect to a new library using foreign functions, right? Is this just an optimization then?

[d-torrance]

I'm a bit confused. Ideally one shouldn't need any changes to the interpreter/engine to connect to a new library using foreign functions, right? Is this just an optimization then?

Correct. This is so we can call functions from other libraries that might use MPFR. The specific case I have in mind is the ball arithmetic stuff in FLINT. It would be possible to call everything just using double's, but it would be nice to allow for arbitrary precision.