Project Overview

You may do this assignment in OCaml, Python or Ruby. You must use each language at least once (over the course of PA2 - PA5); you will use one language (presumably your favorite) twice.

You may work in a team of two people for this assignment. You may work in a team for any or all subsequent programming assignments. You do not need to keep the same teammate. The course staff are not responsible for finding you a willing teammate. However, you must still satisfy the language breadth requirement (i.e., you must be graded on at least one OCaml program, at least one Ruby program, and at least one Python program).

Goal

You will also write additional code to unserialize the class map, implementation map, parent map, and annotated AST produced by the semantic analyzer.

The Specification

1. A program that takes a single command-line argument (e.g., file.cl-type). That argument will be an ASCII text Cool class map, implementation map, parent map and annotated AST file (as described in PA4). Your program must emit file.cl-asm, a Cool Assembly Language program. Executing file.cl-asm in a Cool CPU Simulator must produce the correct output for file.cl according to Cool's operational semantics. Your program will consist of a number of OCaml files, a number of Python files, or a number of Ruby files.
   • You will only be given .cl-type files from programs that pass the semantic analysis phase of the reference compiler. You are not responsible for correctly handling (1+"hello") programs.
2. A plain ASCII text file called readme.txt describing your design decisions and choice of test cases. See the grading rubric. A few paragraphs should suffice.
3. Testcases test1.cl, test2.cl, test3.cl and test4.cl. The testcases should exercise compiler and run-time error corner cases.

Cool Assembly Language

The Cool Reference Manual describes COOL-ASM in detail.

Error Reporting

However, you must generate file.cl-asm so that it checks for and reports run-time errors. When your file.cl-asm program detects an error, it should use the Syscall IO.out_string and Syscall exit assembly instructions to cause an error string to be printed to the screen.

To report an error, write the string ERROR: line_number: Exception: message using Syscall IO.out_string output and terminate the program with Syscall exit. You may generate your file.cl-asm so that it writes whatever you want in the message, but it should be fairly indicative. Example erroneous input:

class Main inherits IO {
  my_void_io : IO ; -- no initializer => void value
  main() : Object {
    my_void_io.out_string("Hello, world.\n")
  } ;
} ;

For such an input, you must generate a well-formed file.cl-asm assmebly language file. However, when that file is executed in a Cool CPU Simulator, it will produce output such as:

ERROR: 4: Exception: dispatch on void

• Stack overflow: undefined (not your responsibility)
• Division by zero: location of the division expression
• Substring out of range: location of the internal expression (i.e., 0)
• Dispatch on void: location of dispatch expression
• case-related errors: location of case expression

Commentary

You can do basic testing as follows:

• $ cool --asm file.cl-type
  $ cool file.cl-asm >& reference-output
  $ my-code-generator file.cl-type 
  $ cool file.cl-asm >& my-output
  $ diff my-output reference-output
  

Whitespace and newlines do not matter in your file.cl-asm assembly code. However, whitespace and newlines do matter for your simulated Cool CPU output. This is because you are specifically being asked to implement IO and substring functions.

You should implement all of the operational semantics rules in the Reference Manual. You will also have to implement all of the built-in functions on the five Basic Classes.

What To Turn In For PA5

1. readme.txt -- your README file
2. test1.cl -- a testcase
3. test2.cl -- a testcase
4. test3.cl -- a testcase
5. test4.cl -- a testcase
6. source_files -- your implementation, including
   • main.rb or
   • main.py or
   • main.ml

• team.txt -- an optional file listing your other team member (see below -- if you are not working in a team, do not include this file)

Working In Pairs

Students on a team are expected to participate equally in the effort and to be thoroughly familiar with all aspects of the joint work. Both members bear full responsibility for the completion of assignments. Partners turn in one solution for each programming assignment; each member receives the same grade for the assignment. If a partnership is not going well, the teaching assistants will help to negotiate new partnerships. Teams may not be dissolved in the middle of an assignment.

If you are working in a team, exactly one team member should submit a PA5 zipfile. That submission should include the file team.txt, a one-line flat ASCII text file that contains exactly and only the email address of your teammate. Don't include the @virgnia.edu bit. Example: If ph4u and wrw6y are working together, ph4u would submit ph4u-pa5.zip with a team.txt file that contains the word wrw6y. Then ph4u and wrw6y will both receive the same grade for that submission.

Autograding

In each case we will then compare your output to the correct answer:

• diff testcase.out correct-answer.out

For error messages and negative testcases we will compare your output but not the particular error message. Basically, your generated code need only correctly identify that there is an error on line X. You do not have to faithfully duplicate our English error messages. Many people choose to (because it makes testing easier) -- but it's not required.

We will perform the autograding on some unspecified test system. It is likely to be Solaris/UltraSPARC, Cygwin/x86 or Linux/x86. However, your submissions must officialy be platform-independent (not that hard with a scripting language). You cannot depend on running on any particular platform.

There is more to your grade than autograder results. See the Programming Assignment page for a point breakdown.

Your submission may not create any temporary files. Your submission may not read or write any files beyond its input and output. We may test your submission in a special "jail" or "sandbox".