Assignment 3

The files for this assignment can be found in h3.tar. Download this file and extract the files. (They will be extracted to a directory called h3)

Here is a new and improved Makefile by John Ratcliff.

Commands to extract, compile, and run are the same as for the previous assignment.

Assignment

The relevant files for the assignment are:

mlexer.mll - the specification of the lexical analyzer
mparser.mly - the specification of the parser
absyn.ml - contains the grammar for abstract syntax of expressions to be manipulated
main.ml - the top level
util.ml - a file with one trivial general function
Makefile - the makefile
tests - a few simple test cases
interpret.ml - contains the beginnings of your solution
interpret.mli - interface file for interpret.ml

This program will evaluate simple Scheme expressions. As in the previous assignment, your code will start with the output of the parser. See absyn.ml for the type information of these expressions. Currently, interpret.ml contains most of the code needed to evaluate the expressions, with only a few cases left to be done.

The interface file, interpret.mli, gives the types of the procedures used in interpret.ml.

For this assignment, you should do the following.

Finish the code for eval, the static scope interpreter.
Write a new evaluation procedure, called evald that will use dynamic scope, rather than static scope as before.

Some solutions for implementing letrec require a small change to the interface file interp.mli. Feel free to use modify the interface in that case.

Submission

Turn in the file interpret.ml on the electronic submission page.