Allow fmpq(fmpq, fmpq) constructor

src/flint/test/test_all.py

@@ -782,6 +782,11 @@ def test_fmpq():
     assert Q(-2,-4) == Q(1,2)
     assert Q("1") == Q(1)
     assert Q("1/2") == Q(1,2)
+    assert Q(Q(1,2),Q(3,4)) == Q(2,3)
+    assert Q(1,Q(2,3)) == Q(3,2)
+    assert Q(Q(1,2),3) == Q(1,6)
+    assert Q(flint.fmpz(1),Q(2,3)) == Q(3,2)
+    assert Q(Q(1,2),flint.fmpz(3)) == Q(1,6)
     assert raises(lambda: Q("1.0"), ValueError)
     assert raises(lambda: Q("1.5"), ValueError)
     assert raises(lambda: Q("1/2/3"), ValueError)

src/flint/types/fmpq.pyi

@@ -14,7 +14,7 @@ class fmpq(flint_scalar):
     @overload
     def __init__(self, arg: ifmpq | _str, /) -> None: ...
     @overload
-    def __init__(self, num: ifmpz, den: ifmpz, /) -> None: ...
+    def __init__(self, num: ifmpq, den: ifmpq, /): ...
 
     @property
     def p(self) -> fmpz: ...

src/flint/types/fmpq.pyx

@@ -94,10 +94,27 @@ cdef class fmpq(flint_scalar):
 
         p2 = any_as_fmpz(p)
         if p2 is NotImplemented:
-            raise TypeError("cannot create fmpq from object of type %s" % type(p))
+            # Allow fmpq(fmpq, fmpq/fmpz)
+            p2 = any_as_fmpq(p)
+            if p2 is NotImplemented:
+                raise TypeError("cannot create fmpz/fmpq from object of type %s" % type(p))
+            q2 = any_as_fmpq(q)
+            if q2 is NotImplemented:
+                raise TypeError("cannot create fmpz/fmpq from object of type %s" % type(q))
+            p3 = p2 / q2
+            fmpq_set(self.val, (<fmpq>p3).val)
+            return
+
         q2 = any_as_fmpz(q)
         if q2 is NotImplemented:
-            raise TypeError("cannot create fmpq from object of type %s" % type(q))
+            # fmpq(fmpz, fmpq)
+            q2 = any_as_fmpq(q)
+            if q2 is NotImplemented:
+                raise TypeError("cannot create fmpz/fmpq from object of type %s" % type(q))
+            p3 = p2 / q2
+            fmpq_set(self.val, (<fmpq>p3).val)
+            return
+
         if fmpz_is_zero((<fmpz>q2).val):
             raise ZeroDivisionError("cannot create rational number with zero denominator")