Rename MPolynomialRing_generic -> MPolynomialRing_base

[jdemeyer]

The name MPolynomialRing_generic is confusing because it's not a generic implementation: it's essentially an abstract base class. One cannot create elements of it:

sage: from sage.rings.polynomial.multi_polynomial_ring_generic import MPolynomialRing_generic
sage: R = MPolynomialRing_generic(ZZ, 2, ["a", "b"], "lex")
sage: R()
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)
<ipython-input-5-5a32ac3184a1> in <module>()
----> 1 R()

/usr/local/src/sage-git/local/lib/python2.7/site-packages/sage/structure/parent.pyx in sage.structure.parent.Parent.__call__ (build/cythonized/sage/structure/parent.c:9489)()
    899         """
    900         if self._element_constructor is None:
--> 901             raise NotImplementedError(f"cannot construct elements of {self}")
    902         cdef Py_ssize_t i
    903         cdef R = parent(x)

NotImplementedError: cannot construct elements of Multivariate Polynomial Ring in a, b over Integer Ring

Typically, the word "generic" means an implementation which works over any ring, for example:

sage: type(matrix(QQbar, 2, 2))
<type 'sage.matrix.matrix_generic_dense.Matrix_generic_dense'>

In two cases, the import of MPolynomialRing_generic was simply removed because it was not used.

Component: basic arithmetic

Author: Jeroen Demeyer

Branch/Commit: fc2a02c

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/25563

[jdemeyer]

Branch: u/jdemeyer/rename_mpolynomialring_generic____mpolynomialring_base

[jdemeyer]

New commits:

fc2a02c

Rename MPolynomialRing_generic -> MPolynomialRing_base

[jdemeyer]

Commit: fc2a02c

[tscrim]

Reviewer: Travis Scrimshaw

[tscrim]

comment:4

Makes sense. LGTM.

[vbraun]

Changed branch from u/jdemeyer/rename_mpolynomialring_generic____mpolynomialring_base to fc2a02c