Due Date: Thursday, February 29, 2024 @ 11:59pm
This project is intended to give you experience constructing a top-down, recursive-descent parser.
Your task is to construct a parser that accepts the PLp1 programming language. Your code will emit the rules that are matched in the code in the order in which they are matched.
I have provided a Java method match in parser/Plp1Parser.java. That routine will match the next input token to the token value passed as a parameter. If the token is required to match, a ParseError is thrown if the input is not the provided token. If the token is not required to match, then the input is unput so that it may be read again.
The interface to the parser is
/**
* Parse the input that has been added to this object
* @return the rules that are applied to parse the input string
*/
public String parse();I also have provided a main() method in Plp1Parser.java. This may be used to invoke the parser from the command line or via the debugger. The input parameters are concatenated to form the input string.
Construct a top-down, recursive-descent parser from the PLp1 grammar found in the PLp1 language description. Your code must emit the rules used to derive the input. As you determine which production to apply, you need to emit a string representation of the rule. You may compute FIRST sets to allow you to deterministically determine what rule is to be expanded at each point in the derivation. As an example, the output for
(+ 2 3)
is
constantExp -> <INTNUM>
expression -> constantExp
constantExp -> <INTNUM>
expression -> constantExp
expression -> <LP> <PLUS> expression expression <RP>
program -> (functionDef | expression)+
When an error is discovered, the words "Parse Error" should be appended to the output string and parsing should stop. For example, the output for
(+ 2)
is
constantExp -> <INTNUM>
expression -> constantExp
Parse Error
Your code must be written in Java. Put all of your code in Plp1Parser.java.
There are no hidden data for this project. All input is provided as JUnit 4 test files in the src/test directory. As in the previous assignment, the commands make test_basic, make test_errors, and make test_adv will execute the test cases.
Submit your code via git as in the previous assignment.