CFWAE Interpreter

In class we have discussed a simple interpreter that can evaluate arithmetic expressions, and added conditionals and functions. Now that we have identifiers, we can implement a full programming language.

We will implement a variant of the CFWAE language, described on the PL online page. You must also define two functions parse and interp, these must be typed as specified in the CFWAE template I have provided on github. The template also defines the datatypes you must use. For this assignment, we will not use desugaring to implement any feature. All features must be defined in the core language and core interpeter.

The pyret reader (sexpr parser) is a little different than racket’s so we will modify the CFWAE grammar to use ( and ) instead of { and } to delimit expressions.

<CFWAE> ::= <num>
    | (+ <CFWAE> <CFWAE>)
    | (- <CFWAE> <CFWAE>)
    | (* <CFWAE> <CFWAE>)
    | (/ <CFWAE> <CFWAE>)
    | <id>
    | (if0 <CFWAE> <CFWAE> <CFWAE>)
    | (with ((<id> <CFWAE>) ...) <CFWAE>)
    | (fun (<id> ...) <CFWAE>)
    | (<CFWAE> <CFWAE> ...)

where an id is not +, -, *, /, with, if0 or fun.

Remember that 20% of your grade will be determined by your comments, documentation, and style. Another 20% will be determined by your test cases. The remaining 60% will be determined by the functionality of your code.