Assigned: Friday, 30 January 2004
Due:Monday, 9 February 2004
Summary: In this stage of the project, you will design and build the lexical analyzer for your Pascal compilers.
Warning: You may be required to use each others' lexers at the next stage of the project.
Warning: You will be working on this stage of the project at the same time you are learning the theory of lexical analysis. This simulataneous work is an experiment suggested by the previous session of the class.
Note: In past sessions of CSC362, I've given students a lot of freedom on the various stages of the project. This year, I'm giving students much less freedom in the hopes that greater guidance will lead to greater success.
Group Work: You should work in groups of size 3. For this stage, you can choose your own groups. I am likely to reassign groups for the next stage of the project.
1. Begin by identifying the natural tokens for Pascal. You should do this by Monday. The Pascal User Manual and Report is a good place to start.
2. Examine the classes in
rebelsky.compiler.lexer. Identify the roles (or potential roles)
each class plays. You
may find it useful to look at
3. Implement the lexical analyzer (yeah, you knew there had to be a
hard part, didn't you?). You should call your lexical analyzer
PascalTokenizer. It should implement the
rebelsky.compiler.lexer.TokenStream interface. The
constructor for your class should take a
rebelsky.compiler.misc.CharStream as input.
4. Write a test program that reads in files and prints out their tokens
(and, possibly, reports on errors as it encounters them). You might want
as a starting point for your explorations.
You are free to implement the lexical analyzer in one of two ways.
You can modify and extend
StupidTokenizer.java. This option is probably the most
straightforward and easiest. However, you will have to deal with
some subtleties of my code and consider the differences between STUPID
You can throw away my code and hand code the analyzer. This solution potentially gives you the most freedom (and perhaps even efficiency). For example, you can probably deal with some non-regular issues with this solution.
In addition, if you have the inclination and lots and lots of spare time, you can write your own lexical analyzer generator. You'll certainly learn a lot of lexical analysis, regular expressions, and automata if you choose this solution. If you choose this option, you should do it in addition to the other options.
Wednesday, 28 January 2004 [Samuel A. Rebelsky]
I usually create these pages
on the fly, which means that I rarely
proofread them and they may contain bad grammar and incorrect details.
It also means that I tend to update them regularly (see the history for
more details). Feel free to contact me with any suggestions for changes.
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