Remove floor, ceiling for integer symbols

Original Intent

Allow optimizations by SymPy when we know that a TypedSymbol is_integer or is_real (e.g. drop rounding functions).

We can deduce some of those properties with Numpy's type system (https://docs.scipy.org/doc/numpy-1.13.0/reference/arrays.scalars.html). We have to be careful since all the is_* methods have ternary logic (True, False, None== we don't know).

Field.Access can take advantage of those optimizations by making it a subclass of TypedSymbol.

Extended Changes

By writing a test I realized that it would be handy to compare AssignmentCollections and use the functions find, match, subs, replace of SymPy.

pystencils/simp/assignment_collection.py

@@ -362,6 +362,34 @@ class AssignmentCollection:
         self.sub_expressions = [Assignment(k, v)
                                 for k, v in sub_expressions_dict.items()]
 
+    def find(self, *args, **kwargs):
+        return set.union(
+            *[a.find(*args, **kwargs) for a in self.all_assignments]
+        )
+
+    def match(self, *args, **kwargs):
+        rtn = {}
+        for a in self.all_assignments:
+            partial_result = a.match(*args, **kwargs)
+            if partial_result:
+                rtn.update(partial_result)
+        return rtn
+
+    def subs(self, *args, **kwargs):
+        return AssignmentCollection(
+            main_assignments=[a.subs(*args, **kwargs) for a in self.main_assignments],
+            subexpressions=[a.subs(*args, **kwargs) for a in self.subexpressions]
+        )
+
+    def replace(self, *args, **kwargs):
+        return AssignmentCollection(
+            main_assignments=[a.replace(*args, **kwargs) for a in self.main_assignments],
+            subexpressions=[a.replace(*args, **kwargs) for a in self.subexpressions]
+        )
+
+    def __eq__(self, other):
+        return set(self.all_assignments) == set(other.all_assignments)
+
 
 class SymbolGen:
     """Default symbol generator producing number symbols ζ_0, ζ_1, ..."""