Machine Problem 4: Modifying an Interpreter

Out: Friday, 8 February 2008

Due: 5 PM Friday, 15 February 2008

Submission: Partners

This assignment is to be done in pairs. If you cannot find a partner, please contact your instructor.

Purpose

The main goal of this assignment is to give you some experience with interpreters for the languages we use to illustrate basic concepts of programming languages.

Tasks

1. [15pts] Extend the provided interpreter for the LET language by making all changes necessary to implement and to test the extensions described by EoPL exercises 3.8, 3.9, and 3.16. Don't forget to change the comments that will need changing, and don't forget to add tests for every new feature of the language.
2. [2pts] Is it possible to write a program in the LET language (as extended by task 1) that gets into an infinite loop and runs forever? Write a short justification of your answer.
3. [6pts] EoPL exercises 3.20 and 3.23. You might want to test your solutions to these exercises using an interpreter for the PROC language, not the LET language.
4. [2pts] Is it possible to write a program in the PROC language PROC language, that gets into an infinite loop and runs forever? Write a short justification of your answer.
5. [4pts] Modify the provided interpreter for the PROC language to use dynamic scoping (as defined in EoPL exercise 3.28) instead of lexical scoping. Note that this is easier than EoPL exercise 3.28 because we aren't asking you to do it twice. (Hint: The procedure operation will ignore its third argument, and the apply-procedure operation will need to take a third argument.) Don't forget to change the comments and tests that will need changing.
6. [1pt] EoPL exercise 3.29. (Hint: You don't have to do any programming for this task, and you can add an argument b to p without changing the nature of the question.)
7. [5pts] Submit a photograph of yourself (preferably in the form of a jpeg or similar file), suitable for public display in the course photo gallery. Alternatively, submit a request to be excused from this requirement (in the form of a plain text file named request.txt).

• interpreter for the LET language
• interpreter for the PROC language

The easiest way to copy these interpreters into one of your own directories is to use the cp command on a CCIS Solaris machine:

        cp -r /course/csg111/.www/interps/let-lang .
        cp -r /course/csg111/.www/interps/proc-lang .

Deliverables

1. A complete interpreter for the LET language with all of the extensions you implement for task 1. You should submit all of the files needed to run your extended interpreter, even if some of those files are exactly the same as the files provided by the instructors.
2. A text file mp4.txt that contains your answers for tasks 2, 3, 4, and 6.
3. A complete interpreter for the PROC language with the dynamic scoping you implement for task 5. You should submit all of the files needed to run your modified interpreter, even if some of those files are exactly the same as the files provided by the instructors.
4. A Development Diary
5. A digital picture of yourself for display in the course photo gallery, or a request to be excused from this requirement.

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Last modified: 8 February 2008