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Apply const liberally.

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This commit is contained in:
Thomas Harte 2025-01-28 18:26:34 -05:00
parent da1d52033b
commit d7b7152315
1 changed files with 13 additions and 9 deletions
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22
Numeric/Carry.hpp
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@ -21,7 +21,8 @@ enum class Operation {
/// • carry after calculating @c lhs + @c rhs if @c is_add is true; or
/// • borrow after calculating @c lhs - @c rhs if @c is_add is false;
/// producing @c result.
template <Operation operation, int bit, typename IntT> bool carried_out(IntT lhs, IntT rhs, IntT result) {
template <Operation operation, int bit, typename IntT>
constexpr bool carried_out(const IntT lhs, const IntT rhs, const IntT result) {
// Additive:
//
// 0 and 0 => didn't.
@ -33,10 +34,9 @@ template <Operation operation, int bit, typename IntT> bool carried_out(IntT lhs
// 1 and 0 => didn't
// 1 and 1 or 0 and 0 => did if 1.
// 0 and 1 => did.
if constexpr (operation == Operation::Subtract) {
rhs = ~rhs;
}
const bool carry = IntT(1 << bit) & (lhs | rhs) & ((lhs & rhs) | ~result);
static_assert(operation == Operation::Add || operation == Operation::Subtract);
const auto adj_rhs = (operation == Operation::Subtract) ? ~rhs : rhs;
const bool carry = IntT(1 << bit) & (lhs | adj_rhs) & ((lhs & adj_rhs) | ~result);
if constexpr (operation == Operation::Subtract) {
return !carry;
} else {
@ -48,21 +48,24 @@ template <Operation operation, int bit, typename IntT> bool carried_out(IntT lhs
/// • @c lhs + @c rhs; or
/// • @c lhs - @c rhs;
/// producing @c result.
template <int bit, typename IntT> bool carried_in(IntT lhs, IntT rhs, IntT result) {
template <int bit, typename IntT>
constexpr bool carried_in(const IntT lhs, const IntT rhs, const IntT result) {
// 0 and 0 or 1 and 1 => did if 1.
// 0 and 1 or 1 and 0 => did if 0.
return IntT(1 << bit) & (lhs ^ rhs ^ result);
}
/// @returns An int of type @c IntT with only the most-significant bit set.
template <typename IntT> constexpr IntT top_bit() {
template <typename IntT>
constexpr IntT top_bit() {
static_assert(!std::numeric_limits<IntT>::is_signed);
constexpr IntT max = std::numeric_limits<IntT>::max();
return max - (max >> 1);
}
/// @returns The number of bits in @c IntT.
template <typename IntT> constexpr int bit_size() {
template <typename IntT>
constexpr int bit_size() {
return sizeof(IntT) * 8;
}
@ -71,10 +74,11 @@ template <typename IntT> constexpr int bit_size() {
/// • @c lhs - @c rhs (if @c is_add is false)
/// and the result was @c result. All other bits will be clear.
template <Operation operation, typename IntT>
IntT overflow(IntT lhs, IntT rhs, IntT result) {
constexpr IntT overflow(const IntT lhs, const IntT rhs, const IntT result) {
const IntT output_changed = result ^ lhs;
const IntT input_differed = lhs ^ rhs;
static_assert(operation == Operation::Add || operation == Operation::Subtract);
if constexpr (operation == Operation::Add) {
return top_bit<IntT>() & output_changed & ~input_differed;
} else {