Ticket #13184: trac_13184_sage_5.9.beta.patch

sage/categories/homset.py

@@ -68 +68 @@
 import morphism
 from sage.structure.parent import Parent, Set_generic
 from sage.misc.lazy_attribute import lazy_attribute
-from sage.misc.cachefunc import cached_function
 import types
 
 ###################################
@@ -157 +156 @@
 
     TESTS:
 
+    Homset are unique parents::
+
+        sage: k = GF(5)
+        sage: H1 = Hom(k,k)
+        sage: H2 = Hom(k,k)
+        sage: H1 is H2
+        True
+
     Some doc tests in :mod:`sage.rings` (need to) break the unique parent
     assumption. But if domain or codomain are not unique parents, then the hom
-    set won't fit. That's to say, the hom set found in the cache will have a
+    set will not fit. That is to say, the hom set found in the cache will have a
     (co)domain that is equal to, but not identic with, the given (co)domain.
 
     By :trac:`9138`, we abandon the uniqueness of hom sets, if the domain or
@@ -227 +234 @@
 
     try:
         # Apparently X._Hom_ is supposed to be cached
-        return X._Hom_(Y, category)
+        # but it is not in some cases (e.g. X is a finite field)
+        # To be investigated
+        H = X._Hom_(Y,category)
+        _cache[key] = H
+        return H
     except (AttributeError, TypeError):
         pass
 

sage/modules/vector_space_homspace.py

@@ -193 +193 @@
 import inspect
 import sage.matrix.all as matrix
 import sage.modules.free_module_homspace
-import vector_space_morphism
 
 # This module initially overrides just the minimum functionality necessary
 # from  sage.modules.free_module_homspace.FreeModuleHomSpace.
@@ -333 +332 @@
 
             sage: U = QQ^3
             sage: V = QQ^4
-            sage: W = QQ^3
+            sage: W = FreeModule(QQ,3,sparse=True)
             sage: X = QQ^4
             sage: H = Hom(U, V)
             sage: K = Hom(W, X)
+            sage: H is K
+            False
 
             sage: A = matrix(QQ, 3, 4, [0]*12)
             sage: f = H(A)
             sage: B = matrix(QQ, 3, 4, range(12))
             sage: g = K(B)
-            sage: f.parent() is g.parent()
-            False
+            sage: f.parent() is H and g.parent() is K
+            True
 
             sage: h = H(g)
             sage: f.parent() is h.parent()
@@ -362 +363 @@
         Previously the above code resulted in a TypeError because the
         dimensions of the matrix were incorrect.
         """
-        import vector_space_morphism
+        from vector_space_morphism import is_VectorSpaceMorphism, VectorSpaceMorphism
         D = self.domain()
         C = self.codomain()
         if matrix.is_Matrix(A):
             pass
-        elif vector_space_morphism.is_VectorSpaceMorphism(A):
+        elif is_VectorSpaceMorphism(A):
             A = A.matrix()
         elif inspect.isfunction(A):
             try:
@@ -393 +394 @@
         else:
             msg = 'vector space homspace can only coerce matrices, vector space morphisms, functions or lists, not {0}'
             raise TypeError(msg.format(A))
-        return vector_space_morphism.VectorSpaceMorphism(self, A)
+        return VectorSpaceMorphism(self, A)
 
     def _repr_(self):
         r"""
@@ -409 +410 @@
             'dimension', '3', 'over', 'Rational', 'Field']
         """
         msg = 'Set of Morphisms (Linear Transformations) from {0} to {1}'
-        return msg.format(self.domain(), self.codomain())
- No newline at end of file
+        return msg.format(self.domain(), self.codomain())