Homework 09: Symbolic Evaluation of Boolean Expressions in Java

Due: 10am WednesdayMonday, March 30April 4, 2011

Overview

Write a Java program boolSimp.dj1dj that reduces boolean expressions (represented in the input and output streams in Scheme-like notation) to simplified form. For the purposes of this assignment, boolean expressions are Scheme expressions constructed from:

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• a Scheme program in the file boolsimp.ss equivalent to the Java program that you are required to write;
• a Java "stub" file boolSimp.dj1dj that defines a composite hierarchy of "abstract syntax" tree classes rooted in the class Form representing boolean expressions;
• a Java library file Parser.java contain a class Parser with
  • a read() method that reads a boolean expression represented in "Scheme form" and returns the corresponsing Java Form abstract syntax tree and
  • a reduce() method that composes the visitors you must write in boolSimp.dj1dj to reduce whatever formula the Parser instance contains to simplified form.
• a Java "stub" test file boolSimpTest.java that includes some rudimentary tests of the code in the boolSimp.dj1dj stub file.

The stub file BoolSimp.dj1dj also includes comments showing you exactly what code you have to write to complete writing your simplifier. Of course, you also need to write corresponding tests and add them to the file BoolSimpTest.java.

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If you omit the new File(...) construction in the argument to Parser and use "<fileName>" instead, you will create a Parser for the String "<fileName>". which is interpreted as a simple boolean variable. The File input format is important because it enables us to conveniently apply your simplifier to formulas that are thousands of symbols long. As a result, you only have to translate the Scheme code in boolsimp.ss into corresponding cleanly-written OO Java code by filling in the gaps in our Java stub file boolSimp.dj1dj. You are expected to appropriately use the composite, interpreter, singleton, and visitor patterns in the code that you write. Since the only stub files that you have to modify are boolSimp.dj1dj and boolSimpTest.java, simply submit expanded versions of these files via OwlSpace to submit your assignment. Warning: we will run your program on large inputs to determine if you wrote the code correctly. Try using the large test files provided on the course wiki.

We have formatted the test files as a .java file rather than a .dj1dj because the Language Levels facility peforms no useful augmentation of JUnit test classes and bypassing the language levels translator avoids some annoying bugs in the implementation of that facility. When using the "Save As" command, please remember to save you file boolSimpTest.java as a .java file not as a .dj1dj file. The "Save" command always retains the file types of all files.

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• boolsimp.ss\ is the reference Scheme program.
• BoolSimp.dj1dj\ is a stub program for a visitor solution.
• BoolSimpTest.java\ is a stub test file for a visitor solution.
• Parser.java\ is a parser file for a visitor solution.
• InterpBoolSimp.dj1dj\ is a stub program for an interpreter solution.
• InterpBoolSimpTest.java\ is a stub test file for an interpreter solution.
• InterpParser.java\ is a parser file for an interpreter solution.

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