|CIT 594 Logo2006 Recognizer
Spring 2006, David Matuszek
In this assignment I define a BNF grammar for a small programming language, which I am calling "Logo 2006". This language is a simplified and modified version of the language Logo.
Your assignment is to write a recognizer for productions in that grammar. A recognizer is a program that, given a stream of tokens and a nonterminal, decides whether or not that stream of tokens is an instance of that nonterminal. The meaning of the production, if any, is outside the scope of this assignment.
For example, one of the nonterminals is
<factor> ::= <NAME> | <NUMBER> | "(" <expression> ")"
The stream of tokens
SYMBOL:( NUMBER:2 SYMBOL:+ NUMBER:3 SYMBOL:)
(the tokenization of the String
"(2+3)") is recognized
by this production.
The complete grammar is on a separate page for easy reference.
For each nonterminal
nt in the grammar (excluding
<EOL>), you should have one
method. Name your methods the same as the nonterminals they recognize. See Recognizer.java for examples, which has the required methods for
<multiplyOperator>, plus some very useful (private) utility methods.
Provide complete JUnit tests for all public methods. Write Javadoc comments for all methods, public and private. Follow all specified style rules.
Caution: Some definitions contains brackets
] as metasymbols, and
<block> also uses
"]" as terminals. Don't
get these confused!
To get started, do the following:
Recognizer.javainto a new project in Eclipse (but don't import
RecognizerTest.java). Also Import... the files you wrote for the Tokenizer assignment.
Recognizerclass, add stubs for each method you will need. This will be one method stub for every nonterminal (
<move>, etc.). Note that you do not need method stubs for
<EOL>, because your tokenizer provides these. You also don't need stubs for my provided methods.
Recognizerclass. Have it generate all the test method stubs for you.
RecognizerTest.javafile into yours. This may involve replacing some constructors or method stubs.
Here's why I suggest the above. If you start by importing my
class, Eclipse won't add test method stubs to it (or if it will, I haven't
yet discovered how). This would mean you would have to write all the test method
stubs by hand, which is boring and error prone. If instead you let Eclipse generate
RecognizerTest.java class, it will be correct and complete, and you can
add code from the provided RecognizerTest.java class simply by cutting and pasting.
I believe you will find that the easiest way to do this assignment is as follows:
RecognizerTest.javainto an actual test. For example,
<comparator>doesn't depend on anything else, but
<comparator>, so write the test code for
Tuesday, February 7, before midnight. Turn in your program via blackboard, and follow these conventions: