# Simplified grammar for testing LBox capabilities.
# LBox<dyn Any> can be used as the abstract syntax type, which effectively
# allows attributes of different types to be associated with grammar symbols.

!use rustlr::{lbup,lbdown,lbget,LBox};
!use crate::Expr::*;
!use std::any::Any;
!
!pub enum Expr {
! Var(String),
! Val(i32),
! Binop(&'static str,LBox<Expr>,LBox<Expr>),
!}
!
! fn main() {} //just so it compiles
!

absyntype LBox<dyn Any>
nonterminal E
nonterminal ES mut
terminals num var + ( ) ;
topsym ES

E --> E:a + E:b {parser.lba(Binop("+",lbdown!(a,Expr),lbdown!(b,Expr)))}
E --> ( E:e ) {e}
E --> num:n {parser.lba(Val(*lbdown!(n,i32)))}
E --> var:v {parser.lba(Var(*lbget!(v,String)))}
ES -->  {parser.lba(Vec::<LBox<Expr>>::new())}
ES ==> ES:es  E:e ; {
   let mut down = lbdown!(es,Vec<LBox<Expr>>);
   down.push(lbdown!(e,Expr));
   lbup!(down)
  } <==


EOF

parser.lba takes any expression and places it inside a LBox<dyn Any> along
with the line, column and source_id numbers that are current to the parser.