/// P-vector addition.
///
/// This function is part of the International Astronomical Union's
/// SOFA (Standards of Fundamental Astronomy) software collection.
///
/// Status: vector/matrix support function.
///
/// Given:
/// ```
/// a double[3] first p-vector
/// b double[3] second p-vector
/// ```
///
/// Returned:
/// ```
/// apb double[3] a + b
/// ```
///
/// Note:
/// It is permissible to re-use the same array for any of the
/// arguments.
pub fn ppp(a: &[f64; 3], b: &[f64; 3]) -> [f64; 3] {
[a[0] + b[0], a[1] + b[1], a[2] + b[2]]
}