GLR parser in Rust.
This crate is most useful when parsers need to be generated at runtime from context-free grammars that depend on user input. In other cases, the [LALRPOP] crate is likely to be more suitable.
This example shows building a parser for the grammar
text
S → S S
S → a
S → ε
and using it to parse the input string a:
```rust use glr::{lalr, Grammar, Parser}; let grammar = Grammar { numsymbols: 2, nonterminals: &[vec![vec![0, 0], vec![1], Vec::new()]], }; let table = lalr::Table::new(&grammar); let (sppf, root) = Parser::new(&grammar, &table) .parse([1]) .okor("Failed to parse")?;
// The family of the root node is three alternative lists of children
let family: Vec<_> = root.family(&sppf).collect();
// Either a single a;
asserteq!(family[0][0].symbol(&sppf), Ok(1));
// left-recursion; or
asserteq!(family[1][0], root);
asserteq!(family[1][1].symbol(&sppf), Err(&[0][..]));
// right recursion.
asserteq!(family[2][0].symbol(&sppf), Ok(0));
assert_eq!(family[2][1], root);
```
Any one of the infinitely many derivation trees can be recovered by unwinding the cycles the right number of times.