lr

A minimal LR parser generator framework designed to (optionally) work alongside relex to build LR parsers that tightly couple with built in types, namely enums.

Examples

Defining grammars on an enum can be handled at compile type by specifying a set of productions, and a goal on variants of an enum.

#[derive(Debug, Lr1, PartialEq)]
pub enum NonTerminal {
    #[goal(r"<E>", reduce_e_unary_non_term)]
    #[production(r"<E> Terminal::Star <B>", |elems| { reduce_e_binary_non_term(2, elems) })]
    #[production(r"<E> Terminal::Plus <B>", |elems| { reduce_e_binary_non_term(3, elems) })]
    #[production(r"<B>", reduce_e_unary_non_term)]
    E(Box<NonTermKind>),
    #[production(r"Terminal::Int", reduce_b_non_term)]
    B(Terminal),
}

Generator types

LR(1)

Currently the generator only supports LR(1) grammars.

Attributes

Attributes for defining a grammar consist of both a rule, which contains the right-hand side of a production within the grammar and a reducer action, which can be either a closure or function following the signature of Fn(&mut Vec<lr_core::TerminalOrNonTerminal<T, NT>) -> Result<NT, String>. Where T and NT represent a terminal and non-terminal symbol in the grammar respectively.

goal

goal defines the final, success state of a parser. When reached the parser will return the tree as returned from this state's reducer.

production

production defines all other grammar rules. Any variant can have as many productions as are necessary.

Warnings

This tool was primarily built to support other projects that shared the same, no dependency goals and restrictions that I am currently working on. Use under the understanding that support for this will be best-effort.