fn sincospi_dd<B: SinCosPiBackend>(
x: f64,
sin_sin_k: DoubleDouble,
sin_cos_k: DoubleDouble,
cos_sin_k: DoubleDouble,
cos_cos_k: DoubleDouble,
backend: &B,
) -> (f64, f64)fn sincospi_dd<B: SinCosPiBackend>(
x: f64,
sin_sin_k: DoubleDouble,
sin_cos_k: DoubleDouble,
cos_sin_k: DoubleDouble,
cos_cos_k: DoubleDouble,
backend: &B,
) -> (f64, f64)