Limits & guarantees

uint128 / int128

• Exact integer arithmetic mod 2^128 (for unsigned) / two's complement representation (signed)
• When __int128 is present, ops use it; otherwise use portable fallback.

Numeric128

• P <= 38
• magnitude must be < 10^P in scaled integer form (after applying scale)
• division by zero => Err::DivByZero

Numeric

• up to 131072 digits before decimal point
• up to 16383 digits after decimal point
• internal base = 1e9 limbs