Update#969
Four functions are implemented forArrayView<MathCell, _> in impl_methods.rs:
zip_cell_with,zip_cell_with_elem,zip_cell_with_same_shape,zip_cell_with_by_rows.
Operator overloading is implemented in impl_ops.rs for the following situations:
ArrayView<MathCell, _> binary_op &ArrayBase
ArrayView<MathCell, _> binary_op Scalar
ArrayView<MathCell, _> assign_op &ArrayBase
ArrayView<MathCell, _> assign_op Scalar

The unresolved problems are:

1. CurrentlyMathCell can only be left value. The main reason are:
   (1) Conflicts occur when compilingMathCell<A> op MathCell<B>
   (2) Rust's orphan rules. We can't write code like this:impl<T> Add<MathCell<T>> for T. This will causeE0210 error

2. The value inMathCell must beCopy
   This is because the value in MathCell needs to be retrieved using theget() method. We cannot get&T from&MathCell<T> unless we create a new structureMathRefCell(RefCell<T>)