68 lines
2.4 KiB
Rust
68 lines
2.4 KiB
Rust
// pest. The Elegant Parser
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// Copyright (c) 2018 Dragoș Tiselice
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//
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// Licensed under the Apache License, Version 2.0
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// <LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0> or the MIT
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// license <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. All files in the project carrying such notice may not be copied,
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// modified, or distributed except according to those terms.
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use crate::ast::*;
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pub fn unroll(rule: Rule) -> Rule {
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let Rule { name, ty, expr } = rule;
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Rule {
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name,
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ty,
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expr: expr.map_bottom_up(|expr| match expr {
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#[cfg(not(feature = "grammar-extras"))]
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Expr::RepOnce(expr) => Expr::Seq(expr.clone(), Box::new(Expr::Rep(expr))),
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Expr::RepExact(expr, num) => (1..num + 1)
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.map(|_| *expr.clone())
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.rev()
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.fold(None, |rep, expr| match rep {
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None => Some(expr),
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Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))),
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})
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.unwrap(),
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Expr::RepMin(expr, min) => (1..min + 2)
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.map(|i| {
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if i <= min {
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*expr.clone()
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} else {
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Expr::Rep(expr.clone())
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}
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})
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.rev()
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.fold(None, |rep, expr| match rep {
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None => Some(expr),
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Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))),
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})
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.unwrap(),
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Expr::RepMax(expr, max) => (1..max + 1)
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.map(|_| Expr::Opt(expr.clone()))
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.rev()
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.fold(None, |rep, expr| match rep {
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None => Some(expr),
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Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))),
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})
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.unwrap(),
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Expr::RepMinMax(expr, min, max) => (1..max + 1)
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.map(|i| {
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if i <= min {
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*expr.clone()
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} else {
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Expr::Opt(expr.clone())
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}
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})
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.rev()
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.fold(None, |rep, expr| match rep {
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None => Some(expr),
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Some(rep) => Some(Expr::Seq(Box::new(expr), Box::new(rep))),
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})
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.unwrap(),
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expr => expr,
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}),
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}
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}
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