My implementation of the Earley parser for syntactic parsing of sentences according to a context-free grammar (CFG). (Implemented for Question #3 of Assignment #2, COMP 599, McGill University.)
Example usage:
python earleyparser.py sample-grammar.txt < sample-sentence.txt
More generally, you can run the parser as follow,
python earleyparser.py <grammer_file>
which reads sentences from standard in, one at a time, printing the parses to standard output using pretty_print(), with parses separated by an extra newline. For sentences that do not have a parse according to the grammar, it prints the sentence back out, unchanged.
Running with the draw option, like so,
python earleyparser.py draw <grammer_file>
displays the parses using NLTK's tree-drawing.
See sample-grammar.txt on how to format your grammar. (The parser program requires each rule to only produce non-terminal or terminal symbols, not both.)
MIT