Modify your interpreter from Homework 3 so that it implements lazy evaluation with cached values, as described in chapter 8 of the PLAI textbook. For example, the expression
{with {x {* 3 4}}
{with {y {/ x 0}}
{* x x}}}
should not crash, because y is never used, and it should only
multiply 3 by 4 once, re-using the same value for the second occurrence
of x.
You are encouraged to do this in teams of two, both students working together on all parts of the assignment; if you do this, turn in one homework with both names on it.