CS 453 Programming Assignment #3 — MiniJava Expression Evaluator

Introduction

1. during the parse of the expression,
2. as a visitor over the abstract syntax tree for the expression, and
3. by generating a MIPS program capable of evaluating the expression.

• build lexers with JLex,
• build parsers with JavaCUP,
• perform syntax-directed evaluation,
• perform syntax-directed translation to an abstract syntax tree (AST),
• use the visitor design pattern, and
• automatically generate a simple MIPS program.

The Assignment

   java -jar ExprEval.jar --one-pass-eval input_file
   
   java -jar ExprEval.jar --two-pass-eval input_file
   
   java -jar ExprEval.jar --two-pass-mips input_file
   

The input_file will contain a single expression followed by a newline. The grammar for the input is as follows:

    Expression ::=
      
        Expression ("+" | "-" | "*" ) Expression

    |   < INTEGER_LITERAL >   
    
    | "(" Expression ")"

For the option --one-pass-eval, the value of the expression should be printed to standard out.

For the option --two-pass-eval, you should generate an AST that is printed to an input_file.ast.dot file and the value of the expression should be computed by visiting the AST. As with the one pass evaluation, the value of the expression should be printed to standard out. We provide you with AST node implementations, an extensible visitor class that traverses all the nodes in the AST in depth-first order, and an example visitor that generates a dot specification of the AST.

When called with the --two-pass-mips option, the expression evaluator should generate an AST that is printed to a input_file.ast.dot file and it should generate a input_file.s file with a MIPS program that evaluates the expression. The MIPS program must be capable of being interpreted by the MARS interpreter.

Getting Started

    MJExprStart/
        Makefile
        
        java-cup-11a.jar
        java-cup-11a-runtime.jar
        
        TestCases/
            expr1.txt		
            expr1.txt.ast.dot	
            expr1.txt.s
            
        java_cup/
            ...
            
        src/
            ExprEvalDriver.java
            ExprEvalMainClass.txt	
            ast_visitors/
                DotVisitor.java
            ast/
                analysis/
                    AnalysisAdapter.java		
                    IAnalysis.java
                    DepthFirstAdapter.java		
                    ReversedDepthFirstAdapter.java

                node/
                    IExp.java		
                    IntegerExp.java		
                    Node.java
                    ISwitch.java		
                    MinusExp.java		
                    PlusExp.java
                    ISwitchable.java	
                    MulExp.java		
                    Token.java

            mjparser/
                TokenValue.java

To pass line and position information from the lexer to the parser. You will need the following information in your .lex file:

package mjparser;
import java_cup.runtime.Symbol;

%%
%cup
%line
%char
%public
...
{number} {return new Symbol(sym.NUMBER, new TokenValue(yytext(), yyline, yychar));}
...

In the .cup file for the parser that generates an AST, you will need to generate AST nodes in the actions. Here is an example:

    expr      ::= NUMBER:n
                  {: RESULT = new IntegerExp(new Token(n.text,n.line,n.pos)); :}

The ast.analysis and ast.node packages will be covered in recitation on Friday. You can use them or organize your program differently. The ast_visitors.DotVisitor class is an example of using the ast.analysis package and can be used as follows:

	        java.io.PrintStream astout =
	          new java.io.PrintStream(
	            new java.io.FileOutputStream(filename + ".ast.dot"));
	            
	        ast_root.apply(new DotVisitor(new PrintWriter(astout)));
	        
	        System.out.println("Printing dot file to " + filename + ".ast.dot");

See example output in the TestCases/ subdirectory of MJExprStart.

To get your code to compile with Eclipse, you will need to put the java-cup-11a-runtime.jar in your build path.

        Project --> Properties --> Java Build Path --> Libraries --> Add Library

Submitting the Assignment

• Make sure you test your implementation thoroughly.
• Only turnin one assignment per group.
• Use subversion to export a copy of your assignment.
• Create the ExprEval.jar file that contains all the source code, the .class files, your .cup and .lex files, a README file, and a subversion.txt file. We should be able to use the jar file to run your expression evaluator.
  • See the Makefile in MJExprStart for an example of how to generate a .jar file. The jar command used in that Makefile does not pack in the source files, so you will need to edit it to sure the *.java files are included in your jar.
  • The README file should include your username(s), emails(s), and any information you want the TA to have before grading your assignment ( e.g., this part is not working due to..., any assumptions you had to make due to ambiguity in the specification, a favorite quote or joke to amuse the TA, etc).
  • The subversion.txt file should include output from the following:

    svn log
    svn info
    svnlook tree REPOSITORY_PATH  svnlook must be issued on a department machine
        

• Submit assignment using checkin utility.

  ~cs453/bin/checkin PA3 PA3_groupname.tar

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