lokeg

  use bumpalo::Bump;
  use std::io::Read;
  fn main() {
      let mut arena = Bump::new();
      loop {
          read_and_process_lines(&mut arena);
          arena.reset();
      }
  }
  #[derive(Debug)]
  enum AstNode<'a> {
      Leaf(&'a str),
      Branch {
          line: &'a str,
          meta: usize,
          cons: &'a mut AstNode<'a>
      },
  }
  fn read_and_process_lines(arena: &Bump) {
      let cap = 40;
      let buf: &mut [u8] = arena.alloc_slice_fill_default(cap);
      let l = std::io::stdin().lock().read(buf).expect("reading stdin");
      let content: &str = str::from_utf8(&buf[..l]).unwrap();
      dbg!(content);

      let mut lines = content.lines();
      let mut latest: &mut AstNode<'_> = arena.alloc(AstNode::Leaf(lines.next().unwrap()));
      for line in lines {
          latest = arena.alloc(AstNode::Branch{line, meta:0, cons: latest});
      }
      println!("{latest:?}");
  }