Merge pull request #421 from magv/fmpq_mpoly_zpoly_ref

Add fmpq_mpoly.zpoly and fmpq_mpoly.zcontent (fixes #419)

Author: oscarbenjamin

.github/workflows/buildwheel.yml

@@ -363,7 +363,6 @@ jobs:
         # Supported Flint versions:
         flint-tag: [
           'v3.0.1',
-          'v3.1.3-p1',
           'v3.2.2',
           'v3.3.1',
           'v3.4.0',

README.md

@@ -144,6 +144,7 @@ Compatible versions:
 
 | python-flint | Release date  | CPython     | FLINT      | Cython           |
 |--------------|---------------|-------------|------------|------------------|
+| `0.10.0`     | Not released  | `3.10-3.15` | `3.0-3.6`  | `3.1-3.3`        |
 | `0.9.0`      |  3rd Jul 2026 | `3.10-3.14` | `3.0-3.6`  | `3.1-3.2`        |
 | `0.8.0`      | 29th Aug 2025 | `3.11-3.14` | `3.0-3.3`  | `3.1` only       |
 | `0.7.0`      | 16th Mar 2025 | `3.11-3.13` | `3.0-3.2`  | `3.0.11-3.1.0a1` |
@@ -163,6 +164,22 @@ experimental.
 CHANGELOG
 =========
 
+0.10.0 (Not yet released)
+-------------------------
+
+Contributors (0.10.0):
+
+- Vitaly Magerya (VM)
+- Oscar Benjamin (OB)
+
+Changes (0.10.0):
+
+- [gh-421](https://github.com/flintlib/python-flint/pull/421),
+  Add `zpoly` and `zcontent` methods to `fmpq_mpoly`, to get
+  the primitive integer polynomial and the `fmpq` content, which
+  form the internal representation of the `fmpq_mpoly`. Also add
+  support for building with Cython 3.3. (VM, OB)
+
 0.9.0
 -----
 

doc/source/build.rst

@@ -84,6 +84,11 @@ Compatible versions:
      - CPython
      - FLINT
      - Cython
+   * - 0.10.0
+     - Not released
+     - 3.10-3.15
+     - 3.0-3.6
+     - 3.1-3.3
    * - 0.9.0
      - 3rd Jul 2026
      - 3.10-3.14

meson.build

@@ -18,7 +18,7 @@ project(
 flint_lower = '>=3.0'
 flint_upper = '<3.7'
 cython_lower = '>=3.0.11'
-cython_upper = '<3.3'
+cython_upper = '<3.4'
 
 py = import('python').find_installation(pure: false)
 

pyproject.toml

@@ -41,7 +41,7 @@ content-type = "text/markdown"
 # fine. It is not possible to have a separate version constraint here for the
 # freethreading build only though.
 #
-requires = ["meson-python >= 0.18", "cython >=3.1,<3.3"]
+requires = ["meson-python >= 0.18", "cython >=3.1,<3.4"]
 build-backend = "mesonpy"
 
 [tool.meson-python]

src/flint/test/test_all.py

@@ -3934,6 +3934,27 @@ def quick_poly():
         assert False # New _mpoly types?
 
 
+def test_fmpq_mpoly_zcontent_zpoly():
+    ctx = flint.fmpq_mpoly_ctx.get(("x", "y"))
+    x, y = ctx.gens()
+    zctx = flint.fmpz_mpoly_ctx.from_context(ctx)
+    zx, zy = zctx.gens()
+
+    f = -2*x/3 - 2*y/5
+    assert f.zcontent() == flint.fmpq(-2, 15)
+    assert f.zpoly() == 5*zx + 3*zy
+    assert isinstance(f.zcontent(), flint.fmpq)
+    assert isinstance(f.zpoly(), flint.fmpz_mpoly)
+    # Can't mix fmpq_mpoly with fmpz_mpoly...
+    p = flint.fmpq_mpoly(f.zpoly(), ctx=ctx)
+    c = f.zcontent()
+    assert p * c == f
+
+    f = 0*x
+    assert f.zcontent() == 0
+    assert f.zpoly() == 0
+
+
 def _all_mpoly_vecs():
     return [(flint.fmpz_mpoly_ctx, flint.fmpz_mpoly_vec), (flint.fmpq_mpoly_ctx, flint.fmpq_mpoly_vec)]
 

src/flint/types/fmpq_mpoly.pyi

@@ -102,6 +102,9 @@ class fmpq_mpoly(flint_mpoly[fmpq_mpoly_ctx, fmpq, ifmpq]):
     def xgcd(self, other: fmpq_mpoly, /) -> fmpq: ...
     def term_content(self) -> fmpq_mpoly: ...
 
+    def zpoly(self) -> fmpz_mpoly: ...
+    def zcontent(self) -> fmpq: ...
+
     def factor(self) -> tuple[fmpq, list[tuple[fmpq_mpoly, int]]]: ...
     def factor_squarefree(self) -> tuple[fmpq, list[tuple[fmpq_mpoly, int]]]: ...
 

src/flint/types/fmpq_mpoly.pyx

@@ -17,7 +17,7 @@ from flint.types.fmpz_vec cimport fmpz_vec
 from flint.types.fmpq_vec cimport fmpq_vec
 
 from flint.types.fmpz cimport fmpz, any_as_fmpz
-from flint.types.fmpz_mpoly cimport fmpz_mpoly
+from flint.types.fmpz_mpoly cimport fmpz_mpoly, fmpz_mpoly_ctx, create_fmpz_mpoly
 
 from flint.flintlib.functions.fmpq cimport fmpq_set, fmpq_one
 from flint.flintlib.functions.fmpq_mpoly cimport (
@@ -215,6 +215,23 @@ cdef class fmpq_mpoly(flint_mpoly):
     """
     The *fmpq_mpoly* type represents sparse multivariate polynomials over
     the rationals.
+
+    Internally, an ``fmpq_mpoly`` is represented as the product of a signed
+    rational content and a primitive integer multivariate polynomial with
+    positive leading coefficient. The :meth:`zcontent` and :meth:`zpoly`
+    methods return copies of these two components, respectively.
+
+    The original polynomial can be reconstructed from these components by
+    converting the integer polynomial back to an ``fmpq_mpoly`` in the
+    original context and multiplying by the content:
+
+        >>> ctx = fmpq_mpoly_ctx.get(("x", "y"))
+        >>> x, y = ctx.gens()
+        >>> f = -2*x/3 - 2*y/5
+        >>> zpoly = f.zpoly()
+        >>> content = f.zcontent()
+        >>> fmpq_mpoly(zpoly, ctx=f.context()) * content == f
+        True
     """
 
     def __cinit__(self):
@@ -785,6 +802,36 @@ cdef class fmpq_mpoly(flint_mpoly):
         fmpq_mpoly_term_content(res.val, self.val, self.ctx.val)
         return res
 
+    def zpoly(self):
+        """
+        Return the integer polynomial of ``self``. The product
+        of this and ``self.zcontent()`` represents the whole
+        polynomial.
+
+            >>> ctx = fmpq_mpoly_ctx.get(("x","y"))
+            >>> x, y = ctx.gens()
+            >>> (x*2/3 + y*2/5).zpoly()
+            5*x + 3*y
+        """
+        cdef fmpz_mpoly_ctx zctx = fmpz_mpoly_ctx.from_context(self.ctx)
+        cdef fmpz_mpoly res = create_fmpz_mpoly(zctx)
+        fmpz_mpoly_set(res.val, self.val.zpoly, zctx.val)
+        return res
+
+    def zcontent(self):
+        """
+        Return the content of ``self``. The product of this and
+        ``self.zpoly()`` represents the whole polynomial.
+
+            >>> ctx = fmpq_mpoly_ctx.get(("x","y"))
+            >>> x, y = ctx.gens()
+            >>> (x*2/3 + y*2/5).zcontent()
+            2/15
+        """
+        cdef fmpq res = fmpq.__new__(fmpq)
+        fmpq_set(res.val, self.val.content)
+        return res
+
     def resultant(self, other, var):
         """
         Return the resultant of ``self`` and ``other`` with respect to variable ``var``.