[[!toc]]
-We're going to make gradual improvements to the calculator we developed in [week7](/reader_monad_for_variable_binding).
+In class on November 22, we just reviewed mutation and aliasing, especially in relation to the Groenendijk, Stockhof and Veltman paper. Below, we bring in more material. This takes the form of making gradual improvements to the calculator we developed in [week7](/reader_monad_for_variable_binding). Part of what we do below is a review of the mutation techniques developed in [[Week9]]; but we also do other things we haven't discussed in class, like defining new complex functions in our calculator.
+
##Original Calculator##