Language λD (now with define)
Note: This section requires functions and structures defined in file hw5-util.rkt. Tests can be found in file test-hw5.rkt.
1. Your goal is to implement the evaluation of expressions using a mutable environment, notation e ⇓E v.
Implement function (d:eval-exp mem env exp), whose contract is defined as
(- mem? handle? d:expression? eff?)
where memory mem is a heap of frames, the environment env is a handle to a frame in the memory, and the expression exp is being evaluated. Function d:eval-exp must return an effect whose state is the possibly modified heap and the result is the evaluated value.
2. Your goal is to implement the evaluation of terms using a mutable environment, notation t ⇓E v. Implement function (d:eval-term mem env term), whose contract is defined as
(- mem? handle? d:term? eff?)
where memory mem is a heap of frames, the environment env is a handle to a frame in the memory, and the term term is being evaluated. Function d:eval-term must return an effect whose state is the possibly modified heap and the result is the evaluated value.
3. Considering how definitions work in Racket and our specification of Language λD, distinguish the variable binding semantics of Language λD from Racket. Give an example of a program that behaves differently in λD and in Racket. We are not interested in features that are implemented in one language but are not in another (say the lack of promises), so only consider programs whose syntax is the same for both λD and Racket.
