Allow optimizations by SymPy when we know that a
(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 (
None== we don't know).
Field.Access can take advantage of those optimizations by making it a subclass of
By writing a test I realized that it would be handy to compare
AssignmentCollections and use the functions
replace of SymPy.