Add adds two int64s and errors if there is an overflow.

Div divides two int64s and throws errors if there are problems.

DivMod calculates the quotient and the remainder of dividing a by b, returns both, and and returns errors if there are issues.

ExpFrac calculates e^x, where x is a fraction numerator/denominator between 0 and 1.

Mod calculates the remainder of dividing a by b and returns errors if there are issues.

Mul multiplies two int64s and errors if there is an overflow.

MulDiv multiplies a int64 value by the ratio n/d without overflowing the int64, provided that the final result does not overflow.

Sub subtracts two int64s and errors if there is an overflow.