Add scalar constructors for Segment3d and document 2D convention

Author: YenPeiChen07

cpp/solvcon/universe/coord.hpp

@@ -34,6 +34,10 @@ enum class Axis : uint8_t
 /**
  * Point in three-dimensional space.
  *
+ * A pad of ndim 2 stores and reports z as zero, and a segment or point read 
+ * back from it carries that zero. Plane code is meant to ignore it, not to 
+ * work around it.
+ *
  * @tparam T floating-point type
  *
  * @ingroup group_geometry
@@ -271,6 +275,10 @@ using Point3dFp64 = Point3d<double>;
  * Coordinates are stored as separate per-axis arrays (x, y, and, for
  * three dimensions, z), so the layout is structure-of-arrays. The
  * dimensionality (2 or 3) is fixed at construction and cannot change.
+ * 
+ * A pad of ndim 2 stores and reports z as zero, and a segment or point read 
+ * back from it carries that zero. Plane code is meant to ignore it, not to 
+ * work around it.
  *
  * @tparam T floating-point type
  *
@@ -751,6 +759,10 @@ union Segment3dData
 
 /**
  * Segment in three-dimensional space.
+ * 
+ * A pad of ndim 2 stores and reports z as zero, and a segment or point read 
+ * back from it carries that zero. Plane code is meant to ignore it, not to 
+ * work around it.
  *
  * @tparam T floating-point type
  *
@@ -773,6 +785,16 @@ class Segment3d
     {
     }
 
+    Segment3d(T x0, T y0, T x1, T y1)
+        : m_data{{x0, x1, y0, y1, 0.0, 0.0}}
+    {
+    }
+
+    Segment3d(T x0, T y0, T z0, T x1, T y1, T z1)
+        : m_data{{x0, x1, y0, y1, z0, z1}}
+    {
+    }
+
     Segment3d() = default;
     Segment3d(Segment3d const &) = default;
     Segment3d & operator=(Segment3d const &) = default;
@@ -904,9 +926,9 @@ using Segment3dFp64 = Segment3d<double>;
 /**
  * Container of line segments in two- or three-dimensional space.
  *
- * Each segment is stored as a pair of endpoints, held in two PointPad
- * objects (one for each endpoint). The dimensionality (2 or 3) comes
- * from the underlying point pads.
+ * A pad of ndim 2 stores and reports z as zero, and a segment or point read 
+ * back from it carries that zero. Plane code is meant to ignore it, not to 
+ * work around it.
  *
  * @tparam T floating-point type
  *

cpp/solvcon/universe/pymod/wrap_shape1d.cpp

@@ -62,6 +62,18 @@ WrapSegment3d<T> & WrapSegment3d<T>::wrap_management()
         .def(py::init<point_type const &, point_type const &>(),
              py::arg("p0"),
              py::arg("p1"))
+        .def(py::init<value_type, value_type, value_type, value_type>(), 
+             py::arg("x0"),
+             py::arg("y0"),
+             py::arg("x1"),
+             py::arg("y1"))
+        .def(py::init<value_type, value_type, value_type, value_type, value_type, value_type>(), 
+             py::arg("x0"),
+             py::arg("y0"),
+             py::arg("z0"),
+             py::arg("x1"),
+             py::arg("y1"),
+             py::arg("z1"))
         //
         ;
 

tests/test_universe_shape1d.py

@@ -21,6 +21,13 @@ def test_construct(self):
         self.assertEqual(tuple(s.p0), (0.0, 0.0, 0.0))
         self.assertEqual(tuple(s.p1), (1.0, 1.0, 1.0))
 
+        s_6scalar = Segment(x0=0, y0=0, z0=0, x1=1, y1=1, z1=1)
+        self.assertEqual(s_6scalar, s)
+
+        s.z1 = 0.0
+        s_4scalar = Segment(x0=0, y0=0, x1=1, y1=1)
+        self.assertEqual(s_4scalar, s)
+
         s.p0 = Point(x=3, y=7, z=0)
         s.p1 = Point(x=-1, y=-4, z=9)
         self.assertEqual(s.x0, 3)