From a brief view on your implementation it seems that there is no way to get access to the internal data, exp, neg, fpclass members. Am I right? Could you expose those as readonly through a const accessor methods? I need this functionality to be able to compare two floating point values within specified ulp range (units in the last place).
We can never expose internal details as such.... since they're details and change from backend to backend. But: exponent - available via frexp, cheap for binary types, expensive for decimal types. neg - Use mp_number::sign(). Comparison with a literal 0 is cheap too (optimized in terms of sign()). fpclass - use boost::math::fpclassify - it's as cheap as it's going to get for that operation. In other words, use the same operations you would as with a builtin floating point type. HTH, John.