README.md

ptb-reader

Natural language processing work on syntax starts with being able to read standard corpora, such as the Penn Treebank. This crate is able to parse the merged (i.e. syntactic structure and POS tags) files of the free sample and the full PTB Wall Street Journal section.

Data types

The output of the parser is a Vec<PTBTree>, PTBTree being defined by:

pub enum PTBTree {
    InnerNode {
        label: String,
        children: Vec<PTBTree>
    },
    TerminalNode {
        label: String
    }
}

PTBTree implements the Display trait, showing the PTB-bracketed notation. It also supports From/Into String, yielding the front of the tree (i.e., the concatenation of all terminals).

Example usage

Parse the whole PTB sample:

let all_trees: Vec<PTBTree> = ptb_reader::parse_ptb_dir("/home/sjm/documents/Uni/penn-treebank-sample/treebank/combined/");

Parse and work with an individual tree:

let s: String = "((S (NNP John) (VP (VBD saw) (NNP Mary))))";
let t: PTBTree = 
    PTBTree::InnerNode{ label: "S".to_string(), children: vec![
        PTBTree::InnerNode{ label: "NNP".to_string(), children: vec![
            PTBTree::TerminalNode{ label: "John".to_string() }
        ] },
        PTBTree::InnerNode{ label: "VP".to_string(), children: vec![
            PTBTree::InnerNode{ label: "VBD".to_string(), children: vec![
                PTBTree::TerminalNode{ label: "saw".to_string() }
            ] },
            PTBTree::InnerNode{ label: "NNP".to_string(), children: vec![
                PTBTree::TerminalNode{ label: "Mary".to_string() }
            ] }
        ] }
    ] }
;
assert_eq!(parse_ptbtree(s).unwrap(), t);
assert_eq!(t.render(), s);
assert_eq!(t.front(), "John saw Mary");

Strip predicate-argument annotations:

let s: &str      = "((S (NNP     John) (VP            (VBD saw) (NNP Mary)              )))";
let s_pred: &str = "((S (NNP-SBJ John) (VP (NP *T*-1) (VBD saw) (NNP Mary) (-NONE- nada))))";

let mut t = parse_ptbtree(s_pred).unwrap();
t.strip_all_predicate_annotations();
assert_eq!(t, parse_ptbtree(s).unwrap())