Module sp_arithmetic::helpers_128bit

Some helper functions to work with 128bit numbers. Note that the functionality provided here is only sensible to use with 128bit numbers because for smaller sizes, you can always rely on assumptions of a bigger type (u128) being available, or simply create a per-thing and use the multiplication implementation provided there.

Functions

gcd	Helper gcd function used in Rational128 implementation.
multiply_by_rational	Safely and accurately compute a * b / c. The approach is:
split	split a u128 into two u64 limbs
to_big_uint	Convert a u128 to a u32 based biguint.