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// pest. The Elegant Parser
// Copyright (c) 2018 Dragoș Tiselice
//
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. All files in the project carrying such notice may not be copied,
// modified, or distributed except according to those terms.

// This structure serves to improve performance over Token objects in two ways:
//
//   * it is smaller than a Token, leading to both less memory use when stored in the queue but also
//     increased speed when pushing to the queue
//   * it finds its pair in O(1) time instead of O(N), since pair positions are known at parse time
//     and can easily be stored instead of recomputed
#[derive(Debug)]
pub enum QueueableToken<R> {
    Start {
        end_token_index: usize,
        input_pos: usize,
    },
    End {
        start_token_index: usize,
        rule: R,
        input_pos: usize,
    },
}