prattle 0.1.3

// precedence.rs - MIT License
//  MIT License
//  Copyright (c) 2018 Tyler Laing (ZerothLaw)
// 
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//! # Precendence Levels
//! This is the most powerful, subtle, and easy to do incorrectly part of the 
//! Pratt parser. Each token has a specific null/left/right binding power, 
//! and to be processed, they need to be higher than the current context
//! 
//! This allows the algorithm/parser to naturally implement precedence climbing
//! which is what basically says X operator is processed before other operators. 
//! 
//! ## Example
//! > a + b * c
//! 
//! When mul is defined with a higher precedence than add, that results in the 
//! following grouping:
//! > a + (b * c)
//! where b*c is done before the addition. Many languages have either a defined
//! or implicit precedence ordering of operators. 
//! 
//! For example, see [C++ Operator Precedence table](https://en.cppreference.com/w/cpp/language/operator_precedence)
//! 

use std::fmt;
use std::fmt::{Display, Formatter};

#[derive(Clone, Copy, Debug, Eq, Hash, Ord, PartialEq, PartialOrd)]
pub enum PrecedenceLevel {
    Root    = 0, 
    First   = 5, 
    Second  = 10, 
    Third   = 15, 
    Fourth  = 20, 
    Fifth   = 25, 
    Sixth   = 30, 
    Seventh = 35, 
    Eighth  = 40,
}

impl Display for PrecedenceLevel {
    fn fmt(&self, f: &mut Formatter) -> Result<(), fmt::Error> {
        write!(f, "(Precedence: {})", *self as u32)
    }
}