- background: for some application it can be useful to have fully
sorted points. i.e., sorted by x, followed by y, followed by z.
The default VectorSpace 'operator<' compares *all*
components. This is seen by the following comparisons
1. a = (-2.2 -3.3 -4.4)
b = (-1.1 -2.2 3.3)
(a < b) : True
Each 'a' component is less than each 'b' component
2. a = (-2.2 -3.3 -4.4)
b = (-2.2 3.3 4.4)
(a < b) : False
The a.x() is not less than b.x()
The static definitions 'less_xyz', 'less_yzx', 'less_zxy'
instead use comparison of the next components as tie breakers
(like a lexicographic sort).
- same type of definition that Pair and Tuple2 use.
a = (-2.2 -3.3 -4.4)
b = (-2.2 3.3 4.4)
vector::less_xyz(a, b) : True
The a.x() == b.x(), but a.y() < b.y()
They can be used directly as comparators:
pointField points = ...;
std::sort(points.begin(), points.end(), vector::less_zxy);
ENH: make VectorSpace named access methods noexcept.
Since the addressing range is restricted to enumerated offsets
(eg, X/Y/Z) into storage, always remains in-range.
Possible to make constexpr with future C++ versions.
STYLE: VectorSpace 'operator>' defined using 'operator<'
- standard rewriting rule
c973066646