extend _coerce_map_from_ in rejecting-subring

sagemath · Sep 20, 2015 · 8696a6e · 8696a6e
1 parent 4b8f9be
commit 8696a6e
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/src/sage/symbolic/subring.py b/src/sage/symbolic/subring.py
@@ -797,9 +797,16 @@ def _coerce_map_from_(self, P):
             False
             sage: R.has_coerce_map_from(RS)  # indirect doctest
             True
+            sage: A = SymbolicSubring(accepting_variables=('a',))
+            sage: R.has_coerce_map_from(A)
+            True
+            sage: A.has_coerce_map_from(R)
+            False
         """
         if isinstance(P, SymbolicSubringRejectingVars):
             return self._vars_ <= P._vars_
+        elif isinstance(P, SymbolicSubringAcceptingVars):
+            return not (self._vars_ & P._vars_)
         return super(SymbolicSubringRejectingVars, self)._coerce_map_from_(P)