Move matroid constructor

From `constructor.py` to within the `Matroid` class in `matroid.pyx`.

src/sage/geometry/hyperplane_arrangement/arrangement.py

@@ -1902,7 +1902,7 @@ def vertices(self, exclude_sandwiched=False):
             ((0, 0), (0, 8), (8, 0), (8, 8))
         """
         import itertools
-        from sage.matroids.constructor import Matroid
+        from sage.matroids.matroid import Matroid
         R = self.parent().base_ring()
         parallels = self._parallel_hyperplanes()
         A_list = [parallel[0][1] for parallel in parallels]
@@ -3202,7 +3202,7 @@ def matroid(self):
         if not self.is_central():
             raise ValueError("the hyperplane arrangement must be central")
         norms = [p.normal() for p in self]
-        from sage.matroids.constructor import Matroid
+        from sage.matroids.matroid import Matroid
         return Matroid(matrix=matrix(norms).transpose())
 
     def orlik_solomon_algebra(self, base_ring=None, ordering=None, **kwds):

src/sage/graphs/graph.py

@@ -9350,7 +9350,7 @@ def arboricity(self, certificate=False):
             sage: g.arboricity(True)                                                    # needs sage.modules
             (0, [])
         """
-        from sage.matroids.constructor import Matroid
+        from sage.matroids.matroid import Matroid
         P = Matroid(self).partition()
         if certificate:
             return (len(P), [self.subgraph(edges=forest) for forest in P])

src/sage/matroids/advanced.py

@@ -26,7 +26,7 @@
         - :class:`RankMatroid <sage.matroids.rank_matroid.RankMatroid>`
 
     Note that you can construct all of these through the
-    :func:`Matroid() <sage.matroids.constructor.Matroid>` function, which is
+    :class:`Matroid() <sage.matroids.matroid.Matroid>` class, which is
     available on startup. Using the classes directly can sometimes be useful
     for faster code (e.g. if your code calls ``Matroid()`` frequently).
 

src/sage/matroids/all.py

@@ -6,7 +6,7 @@
 install_doc(__package__, __doc__)
 
 from sage.misc.lazy_import import lazy_import
-lazy_import('sage.matroids.constructor', 'Matroid')
+lazy_import('sage.matroids.matroid', 'Matroid')
 lazy_import('sage.matroids', 'matroids_catalog', 'matroids')
 del lazy_import
 del install_doc

src/sage/matroids/basis_matroid.pyx

@@ -22,7 +22,7 @@ Construction
 A ``BasisMatroid`` can be created from another matroid, from a list of bases,
 or from a list of nonbases. For a full description of allowed inputs, see
 :class:`below <sage.matroids.basis_matroid.BasisMatroid>`. It is recommended
-to use the :func:`Matroid() <sage.matroids.constructor.Matroid>` function for
+to use the :class:`Matroid() <sage.matroids.matroid.Matroid>` class for
 easy construction of a ``BasisMatroid``. For direct access to the
 ``BasisMatroid`` constructor, run::
 

src/sage/matroids/circuit_closures_matroid.pyx

@@ -12,7 +12,7 @@ A ``CircuitClosuresMatroid`` can be created from another matroid or from a
 list of circuit-closures. For a full description of allowed inputs, see
 :class:`below <sage.matroids.circuit_closures_matroid.CircuitClosuresMatroid>`.
 It is recommended to use the
-:func:`Matroid() <sage.matroids.constructor.Matroid>` function for a more
+:class:`Matroid() <sage.matroids.matroid.Matroid>` class for a more
 flexible construction of a ``CircuitClosuresMatroid``. For direct access to
 the ``CircuitClosuresMatroid`` constructor, run::
 

src/sage/matroids/circuits_matroid.pyx

@@ -8,8 +8,8 @@ as data.
 A ``CircuitsMatroid`` can be created from another matroid or from a list of
 circuits. For a full description of allowed inputs, see
 :class:`below <sage.matroids.circuits_matroid.CircuitsMatroid>`. It is
-recommended to use the :func:`Matroid() <sage.matroids.constructor.Matroid>`
-function for a more flexible way of constructing a ``CircuitsMatroid`` and
+recommended to use the :class:`Matroid() <sage.matroids.matroid.Matroid>`
+class for a more flexible way of constructing a ``CircuitsMatroid`` and
 other classes of matroids. For direct access to the ``CircuitsMatroid``
 constructor, run::