| // 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 ast::*; |
| |
| pub fn unroll(rule: Rule) -> Rule { |
| match rule { |
| Rule { name, ty, expr } => Rule { |
| name, |
| ty, |
| expr: expr.map_bottom_up(|expr| match expr { |
| Expr::RepOnce(expr) => Expr::Seq(expr.clone(), Box::new(Expr::Rep(expr))), |
| Expr::RepExact(expr, num) => (1..num + 1) |
| .map(|_| *expr.clone()) |
| .rev() |
| .fold(None, |rep, expr| match rep { |
| None => Some(expr), |
| Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))), |
| }) |
| .unwrap(), |
| Expr::RepMin(expr, min) => (1..min + 2) |
| .map(|i| { |
| if i <= min { |
| *expr.clone() |
| } else { |
| Expr::Rep(expr.clone()) |
| } |
| }) |
| .rev() |
| .fold(None, |rep, expr| match rep { |
| None => Some(expr), |
| Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))), |
| }) |
| .unwrap(), |
| Expr::RepMax(expr, max) => (1..max + 1) |
| .map(|_| Expr::Opt(expr.clone())) |
| .rev() |
| .fold(None, |rep, expr| match rep { |
| None => Some(expr), |
| Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))), |
| }) |
| .unwrap(), |
| Expr::RepMinMax(expr, min, max) => (1..max + 1) |
| .map(|i| { |
| if i <= min { |
| *expr.clone() |
| } else { |
| Expr::Opt(expr.clone()) |
| } |
| }) |
| .rev() |
| .fold(None, |rep, expr| match rep { |
| None => Some(expr), |
| Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))), |
| }) |
| .unwrap(), |
| expr => expr, |
| }), |
| }, |
| } |
| } |