CS 4550: Translation of Programming Languages

1. A Parser that Recognizes Programs

Your primary task is:

Write a table-driven parser that accepts legal Klein programs.

This parser is a function or object that examines a sequence of Klein tokens to produce a true/false answer: Is the input a legal Klein program?

When created, your parser should either:

• either receive a scanner as an argument
• or receive a source program as an argument and create a scanner on it.

It should provide at least one public function, named parse.

Your parser should implement a table-driven algorithm using a parse table and a stack of states being processed. Your parse table may be implemented in code or in data.

Be sure that your parser detects and reports any syntactic error that prevents it from processing the rest of the program.

• At the bare minimum, the parser can report the combination of non-terminal and token that caused the error. It will be more helpful to the programmer if the parser also reports the next few tokens in the stream.
• Bonus points will be awarded if the parser's error messages report the line and character on which the error occurs, or if the messages provide custom messages for common error states.
• Your parser must catch all error messages generated by your implementation language and report errors as Klein errors. Ideally, the user of your Klein compiler will not know the compiler's implementing language.

2. Klein Programs to Test the Parser

In order to test your parser,

Create five short test programs that are nearly legal but which your program correctly rejects.

Each of these programs should test one interesting cases that your parser ought to recognize as invalid. A nonsense program is less interesting than a program that does something but contains a subtle syntax error.

You should, of course, produce as many tests as you think necessary to ensure that your parser works correctly. You are also encouraged to use any test programs available on the project home page.

3. A Program Validator

Once your parser successfully processes a sequences of tokens:

Write a program that uses your parser to validate a candidate Klein program.

The validator should invoke your parser on the program, and print one of two answers:

• the string valid program
• an error message indicating the one or more errors found by your parser

4. The kleinf Command

Finally,

Create an executable or a Unix command-line script named kleinf that takes the name of a Klein program as an argument and runs your validation program on it.

For example:

$ ./kleinf programs/print-one.kln
valid program

This is the second in a series of tools that makes up the command-line suite of your Klein compiler.

Status Check

You will need to refactor Klein's grammar in order to make it unambiguous before you build your parse table.

Submit:

• your refactored grammar, and
• a list of the changes you made to the grammar.

Make these documents a part of the ongoing documentation of your compiler.

Record your answers in a single file, plaintext or PDF, and email the file to the instructor by the status check due date.

Final Deliverable

By the due time and date, use the course submission system to submit your project directory electronically as a zip file named project02.zip or project02.tar.gz.