Big-Float constants `ee` and `pi` don't change to match precision.

[Izaakwltn]

These variables are locked in with the initial big-float precision, and don't adjust as precision changes.

Initial precision is 53 bits so they're basically locked in as Double-Floats.

[Robert Smith]

note: this is only an issue with the MPFR version of the library. The portable version handles this fine.

[Izaakwltn]

I've been thinking about this bug, and thought of a couple quick but potentially janky approaches for fixing it.

• Every time precision is set, redefine Trigonometric Big-Float and Exponentiable Big-Float, which will automatically update the definition of pi and ee respectively. This could be kept in separate functions like reset-bf-constants or set-precision-and-constants. Bubble-gum and paperclip approach.

  • Note: Is it possible to redefine one member of a type class or does every redefinition have to be applied as a whole?

• Convert Big-Float to MPFR-Float and make a new Big-Float type in the style of impl-default.lisp that uses MPFR-Floats instead of Dyadics. This is probably the nuclear option.

• Simplifying the possibility above, give Big-Float two constructors that contain either an MPFR-Float object or a (Unit -> MPFR-Float) function:

(define-type Big-Float
  (BFValue MPFR-Float)
  (BFConst (Unit -> MPFR-Float))

[Robert Smith]

Ignoring potential language changes, the last suggestion would be the right approach.