pest_meta/optimizer/
rotater.rs

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1// pest. The Elegant Parser
2// Copyright (c) 2018 Dragoș Tiselice
3//
4// Licensed under the Apache License, Version 2.0
5// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
6// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
7// option. All files in the project carrying such notice may not be copied,
8// modified, or distributed except according to those terms.
9
10use crate::ast::*;
11
12pub fn rotate(rule: Rule) -> Rule {
13    fn rotate_internal(expr: Expr) -> Expr {
14        match expr {
15            Expr::Seq(lhs, rhs) => {
16                let lhs = *lhs;
17                match lhs {
18                    Expr::Seq(ll, lr) => {
19                        rotate_internal(Expr::Seq(ll, Box::new(Expr::Seq(lr, rhs))))
20                    }
21                    lhs => Expr::Seq(Box::new(lhs), rhs),
22                }
23            }
24            Expr::Choice(lhs, rhs) => {
25                let lhs = *lhs;
26                match lhs {
27                    Expr::Choice(ll, lr) => {
28                        rotate_internal(Expr::Choice(ll, Box::new(Expr::Choice(lr, rhs))))
29                    }
30                    lhs => Expr::Choice(Box::new(lhs), rhs),
31                }
32            }
33            expr => expr,
34        }
35    }
36
37    let Rule { name, ty, expr } = rule;
38    Rule {
39        name,
40        ty,
41        expr: expr.map_top_down(rotate_internal),
42    }
43}
pest_meta/optimizer/rotater.rs

pest_meta/optimizer/
rotater.rs
