| // pest. The Elegant Parser |
| // Copyright (c) 2018 DragoČ™ 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. |
| |
| use crate::ast::*; |
| |
| pub fn rotate(rule: Rule) -> Rule { |
| fn rotate_internal(expr: Expr) -> Expr { |
| match expr { |
| Expr::Seq(lhs, rhs) => { |
| let lhs = *lhs; |
| match lhs { |
| Expr::Seq(ll, lr) => { |
| rotate_internal(Expr::Seq(ll, Box::new(Expr::Seq(lr, rhs)))) |
| } |
| lhs => Expr::Seq(Box::new(lhs), rhs), |
| } |
| } |
| Expr::Choice(lhs, rhs) => { |
| let lhs = *lhs; |
| match lhs { |
| Expr::Choice(ll, lr) => { |
| rotate_internal(Expr::Choice(ll, Box::new(Expr::Choice(lr, rhs)))) |
| } |
| lhs => Expr::Choice(Box::new(lhs), rhs), |
| } |
| } |
| expr => expr, |
| } |
| } |
| |
| let Rule { name, ty, expr } = rule; |
| Rule { |
| name, |
| ty, |
| expr: expr.map_top_down(rotate_internal), |
| } |
| } |