Exact real arithmetic using a Boehm scaled-integer representation.

Reference: Keith Briggs, Implementing exact real arithmetic in Python, C++ and C. Theor. Comp. Sci.351 (2006), 74–81

Structure representing a real number that is computable to arbitrary precision.

Memoized evaluation of the nth value in the representation

Returns an interval (as a tuple) containing the exact real number; this interval is of approximate width 2^(-n).

Returns -1 if x < y and +1 if x > y

Most significant digit