Rounding & scale

Rounding modes

• Trunc: toward zero.
• HalfUp: if the first dropped digit is >= 5, increment the kept value (preserves sign).

Numeric128

• Scale is compile-time (S).
• Parsing rounds to S.
• mul/div round to S.

Numeric

• Scale is stored per value.
• rescale(new_scale, rnd):
• new_scale > scale: multiply by 10^(delta)
• new_scale < scale: divide by 10^(delta) and apply rounding