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AK: Rename AK::FixedPoint::round to rint and fix a rounding error

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`rint` is a more accurate name for the roudning mode as the fixme above
stated
This commit is contained in:
Hendiadyoin1 2023-07-25 17:53:30 +02:00 • committed by Andrew Kaster
parent 05c959e40b
commit daacc5c6c2
3 changed files with 26 additions and 17 deletions
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14
AK/FixedPoint.h
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@ -99,17 +99,21 @@ public:
return *this;
}
// Note/FIXME: This uses round to nearest break-tie to even
// Not break-tie away from 0 as the C99's round does
constexpr This round() const
constexpr This rint() const
{
// Note: Round fair, break tie to even
Underlying value = m_value >> precision;
// Note: For negative numbers the ordering are reversed,
// and they were already decremented by the shift, so we need to
// add 1 when we see a fract values behind the `.5`s place set,
// because that means they are smaller than .5
// fract(m_value) >= .5?
if (m_value & (1u << (precision - 1))) {
// fract(m_value) > .5?
if (m_value & (radix_mask >> 2u)) {
// yes: round "up";
value += (m_value > 0 ? 1 : -1);
value += 1;
} else {
// no: round to even;
value += value & 1;
@ -134,7 +138,7 @@ public:
: 0));
}
constexpr Underlying lround() const { return round().raw() >> precision; }
constexpr Underlying lrint() const { return rint().raw() >> precision; }
constexpr Underlying lfloor() const { return m_value >> precision; }
constexpr Underlying lceil() const
{