pub fn exp(fp: FpUnit, x: f32) -> f32
e^x: x = n·ln2/64 + r with n the nearest multiple, e^r by its cubic, times 2^((n mod 64)/64) from the table, times 2^(n div 64).
e^x
x = n·ln2/64 + r
n
e^r
2^((n mod 64)/64)
2^(n div 64)