use crate::common::*; pub struct Variables<'a> { stack: Vec<&'a Expression<'a>>, } impl<'a> Variables<'a> { pub fn new(root: &'a Expression<'a>) -> Variables<'a> { Variables { stack: vec![root] } } } impl<'a> Iterator for Variables<'a> { type Item = &'a Token<'a>; fn next(&mut self) -> Option<&'a Token<'a>> { match self.stack.pop() { None | Some(Expression::String { .. }) | Some(Expression::Backtick { .. }) | Some(Expression::Call { .. }) => None, Some(Expression::Variable { token, .. }) => Some(token), Some(Expression::Concatination { lhs, rhs }) => { self.stack.push(lhs); self.stack.push(rhs); self.next() } Some(Expression::Group { expression }) => { self.stack.push(expression); self.next() } } } }