The project has been written in Java. Compile from this directory simply with
javac *.java
To parse using <parser>, where <X> is one of RDParser, LLParser, and
LRParser, run
java <parser> <string>
where <string> is the string to be parsed. The program will output the result
to the screen, and also return success or failure to the terminal in the
conventional fashion; 0 for success, 1 for failure.
For example:
$ java LRParser d+(n/d)*n
The string d+(n/d)*n is VALID!
$ java LRParser d+(n/d)*
The string d+(n/d)* is NOT VALID!
This is contained wholly within the file RDParser.java.
Unfortunately, we could not implement a recursive descent parser with "full
backtracking", so our naive implementation doesn't actually properly recognise
the language for the given grammar; it only correctly recognises a surrounded
in arbitrarily many pairs of parentheses, i.e.
a, (a), ((a)), (((a))), ...
This is contained within the file LLParser.java, with the following class
dependency tree:
LLParserLLParseTableLLStackStack
Noticing that the given grammar is LL(1), the predictive parser we implemented
is an LL(1) parser. It is able to successfully recognise the language given, but
we did not do the additional task of being able to use any int token in place
of a.
This is contained within the file LRParser.java, with the following class
dependency tree:
LRParserLRAutomatonLRStackStack
We wrote an LR parser to serve as a bottom-up parser for the given grammar. It
is able to successfully recognise the language given, but we did not do the
additional task of making int and id correspond to arbitrary integers and
variable names, respectively. Moreover, to simplify the implementation, we don't
use int and id, but instead use n and d, as you may have noticed in the
example given in § Execution:
$ java LRParser d+(n/d)*n
The string d+(n/d)*n is VALID!