panic("x out of range") } if d <= 0 || d >= 12 { panic("d out of range") } precise := big.NewRat((1<<d)*int64(x), q) // (2ᵈ / q) * x == (2ᵈ * x) / q // FloatString rounds halves away from 0, and our result should always be positive, // so it should work as we expect. (There's no direct way to round a Rat.) rounded, err := strconv.ParseInt(precise.FloatString(0), 10, 64) if err != nil { panic(err) } // If we rounded up, `rounded` may be equal to 2ᵈ, so we perform a final reduction. return uint16(rounded...

pkg math/big, method (*Rat) Abs(*Rat) *Rat
pkg math/big, method (*Rat) Add(*Rat, *Rat) *Rat
pkg math/big, method (*Rat) Cmp(*Rat) int
pkg math/big, method (*Rat) Denom() *Int
pkg math/big, method (*Rat) FloatString(int) string
pkg math/big, method (*Rat) GobDecode([]uint8) error
pkg math/big, method (*Rat) GobEncode() ([]uint8, error)
pkg math/big, method (*Rat) Inv(*Rat) *Rat
pkg math/big, method (*Rat) IsInt() bool