- 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
- for most field types this is a no-op, but for a field of floatVector
or doubleVector (eg, vector and solveVector) it will normalise each
element with divide-by-zero protection.
More reliable and efficient than dividing a field by the mag of itself
(even with VSMALL protection).
Applied to FieldField and GeometricField as well.
Eg,
fld.normalise();
vs.
fld /= mag(fld) + VSMALL;
ENH: support optional tolerance for vector::normalise
- for cases where tolerances larger than ROOTVSMALL are preferable.
Not currently available for the field method (a templating question).
ENH: vector::removeCollinear method
- when working with geometries it is frequently necessary to have a
normal vector without any collinear components. The removeCollinear
method provides for clearer, compacter code.
Eg,
vector edgeNorm = ...;
const vector edgeDirn = e.unitVec(points());
edgeNorm.removeCollinear(edgeDirn);
edgeNorm.normalise();
vs.
vector edgeNorm = ...;
const vector edgeDirn = e.unitVec(points());
edgeNorm -= edgeDirn*(edgeDirn & edgeNorm);
edgeNorm /= mag(edgeNorm);
- for use when the is_contiguous check has already been done outside
the loop. Naming as per std::span.
STYLE: use data/cdata instead of begin
ENH: replace random_shuffle with shuffle, fix OSX int64 ambiguity
- this adds support for various STL operations including
* sorting, filling, find min/max element etc.
* for-range iteration
STYLE: use constexpr for VectorSpace rank
- the vector normalise() method modifies the object inplace,
the normalised function returns a copy.
vector vec1(1,2,3);
vec1.normalise();
vs
vector vec1(1,2,3);
vec1 /= mag(vec1) + VSMALL;
For const usage, can use either of these
const vector vec2a(normalised(vector(1,2,3)));
const vector vec2b(vector(1,2,3).normalise());
