handball/src/grammar.lalrpop

use crate::{Tree, Literal, Lambda};
use std::rc::Rc;

grammar<'s>();


pub(crate) Tree: Tree = {
    "(" <Tree+> ")" => Tree::Branch(<>),
    "(" "define" <Sym> <BTree> ")" => Tree::Define(<>),
    "(" "define" "(" <name:Sym> <args:RcSlice<Sym>> ")" <body:Rc<Tree>> ")" => Tree::Define(name, Box::new(Tree::Lambda(Lambda(args, body)))),
    "(" "if" <Tree> <Tree> <Tree> ")" => Tree::If(Box::new([<>])),
    "(" "lambda (" <RcSlice<Sym>> ")" <Rc<Tree>> ")" => Tree::Lambda(Lambda(<>)),
    Literal => Tree::Leaf(<>),
}

BTree = { Box<Tree> }

Literal: Literal = {
    Sym => Literal::Sym(<>),
    Num => Literal::Num(<>),
    Bool => Literal::Bool(<>),
}

Box<T>: Box<T> = { T => Box::new(<>) }
RcSlice<T>: Rc<[T]> = { T* => <>.into() }
Rc<T>: Rc<T> = { T => Rc::new(<>) }

Sym: String = { r"[A-Za-z!$%&*+\-./:<=>?@^_~][A-Za-z!$%&*+\-./:<=>?@^_~0-9]*" => <>.to_owned() }
Num: f64 = { r"[0-9]+(\.[0-9]+)?" => <>.parse().unwrap() }
Bool: bool = { 
    "#t" => true,
    "#f" => false,
}