pub const fn carrying_mul_add<T, U>(
multiplier: T,
multiplicand: T,
addend: T,
carry: T,
) -> (U, T)where
T: CarryingMulAdd<Unsigned = U>,🔬This is a nightly-only experimental API. (
core_intrinsics)Expand description
Performs full-width multiplication and addition with a carry:
multiplier * multiplicand + addend + carry.
This is possible without any overflow. For uN:
MAX * MAX + MAX + MAX
=> (2ⁿ-1) × (2ⁿ-1) + (2ⁿ-1) + (2ⁿ-1)
=> (2²ⁿ - 2ⁿ⁺¹ + 1) + (2ⁿ⁺¹ - 2)
=> 2²ⁿ - 1
For iN, the upper bound is MIN * MIN + MAX + MAX => 2²ⁿ⁻² + 2ⁿ - 2,
and the lower bound is MAX * MIN + MIN + MIN => -2²ⁿ⁻² - 2ⁿ + 2ⁿ⁺¹.
This currently supports unsigned integers only, no signed ones. The stabilized versions of this intrinsic are available on integers.