COP 5621 - Homework 4 - MiniJava Abstract Syntax

Due Wednesday, October 27

In this assignment, we will add actions to our MiniJava parsers to build abstract syntax trees, as described on pages 98-100. Especially study the summary of the class constructors on page 99.

Now /homes/smithg/compiler/minijava/chap4 contains quite a few directories and files, but for this assignment you just need to copy your MiniJava.lex into parse/ and extend your MiniJava grammar from Homework 3 with actions to build abstract syntax trees. Study the new skeleton Grm.cup in chap4/parse/ carefully; it demonstrates techniques that you will need for synthesizing the trees.

A few remarks:

• I've included a test file, Preced.java, and the output that my parser produces for it, Preced.out.
• All of the classes in syntaxtree/ (except for Identifier and the list classes like ClassDeclList) have been extended with a pos field to record the position in the source file that corresponds with each piece of abstract syntax. (Positions are briefly discussed on pages 91-93.) These pos fields allow later compiler phases to give precise error messages. See the skeleton Grm.cup for a couple examples of how these pos fields are filled in.
• Details about CUP actions can be found in the reference manual at http://www.cs.princeton.edu/~appel/modern/java/CUP/.
• You may find it helpful to rewrite some of the rules in your grammar to make it easier to generate abstract syntax. For example, I ended up modifying my rules for FormalList and ExpList.

• COP 5621 home page
• Geoffrey Smith's home page