Assignment 3: Parser with AST Generation Solution

This assignment is a follow up to Assignment 2. In this assignment, you are going to insert semantic actions to parsing routines to generate an abstract syntax tree (AST) for the input program.
This assignment requires a correct LL1 or LL2 miniJava grammar. You are encouraged to use your own mjParser0.jj program as the base for this assignment. However, an LL2 grammar for miniJava will be made available to you as well, after all assignment 1 programs are turned in. In either case, add a comment line at the top of your parser program indicating which version of the grammar it is based on, e.g. “This parser is built with my own grammar.”
Name the parser program for this assignment mjParser.jj.
Preparation
Download the zip file “hw3.zip” from the D2L website. After unzipping, you should see an assignment3
directory with the following items:
– hw3.pdf — this document
mjManual14.pdf — the miniJava language manual
mjParser0.jj — a starting version of miniJava parser; it contains only the lexer portion
ast — a directory containing the AST definition program file, Ast.java
tst — a directory containing sample miniJava programs and their corresponding AST dump outputs
Makefile — for building the parser
runp — a script for running tests
 mjLL2Grammar.txt — an LL(2) miniJava grammar (This file will be released separately, after all
assignment 2 programs are turned in.)
Details
The following are suggested steps to complete this assignment.
1. Complete Lab 6. This week’s lab serves as a warm-up for this assignment. It’s important that you finish the lab first.
2. Familiarize yourself with the AST class definitions, especially the constructors. In your parser program, you’ll insert semantic actions to create AST nodes. Knowing what your choices are and what exact forms you need to follow will be very useful. Look inside the program, ast/Ast.java, to see the AST nodes’ details.
3. Decide a return type for each parsing routine. In Assignment 2’s parser program, parsing routines do not return anything. In the new version for this assignment, all parsing routines participate in the construction of an AST; each routine contributes its share by returning an AST object. Here is a rough guidance for return types (Details depend on your exact grammar.):
1
Parsing Routine Return Type
Program() Ast.Program
ClassDecl() Ast.ClassDecl
MethodDecl() Ast.MethodDecl
Param() Ast.Param
VarDecl() Ast.VarDecl
Any Type routine Ast.Type
Any Stmt routine Ast.Stmt
Any Expr routine Ast.Exp
Id() String
IntLit() int
BoolLit() boolean
Note that three of the return types, Ast.Type, Ast.Stmt, and Ast.Exp, are abstract classes.
Any routine returning these types need to return an object of a concrete subclass of them (e.g. Ast.IntType).
4. Insert semantic actions into the parsing routines. You may want to start with the simpler ones first.
Most statement routines have direct corresponding AST nodes, so they are easy to handle. Binary and unary operation routines are also easy to handle. The more difficult routines are those involving ExtId, since they cover multiple miniJava constructs, e.g. method calls, assignments, array elements, and object fields. For these routines, you need to analyze each case carefully to decide what type of AST node to return. In some cases, a single routine may need to return different types of AST nodes for different sub cases.
5. Compile and run tests. You can use the Makefile to compile your parser:
linux make
Your program should be free of JavaCC and Java compiler warnings, and it should still detect all miniJava syntax errors as your Assignment 2 program did.
To run a batch of tests from the /tst directory, use the runp script:
linux ./runp mjParser tst/*.java
It will place your parser’s output in *.ast files and use diff to compare them one-by-one with the reference version in .ast.ref files. For each test program, its AST should be unique; therefore, your parser’s output should match the reference copy exactly. You could also manually run a single test:
linux java mjParser tst/test01.java