Enum pest_meta::ast::Expr

pub enum Expr {
    Str(String),
    Insens(String),
    Range(String, String),
    Ident(String),
    PeekSlice(i32, Option<i32>),
    PosPred(Box<Expr>),
    NegPred(Box<Expr>),
    Seq(Box<Expr>, Box<Expr>),
    Choice(Box<Expr>, Box<Expr>),
    Opt(Box<Expr>),
    Rep(Box<Expr>),
    RepOnce(Box<Expr>),
    RepExact(Box<Expr>, u32),
    RepMin(Box<Expr>, u32),
    RepMax(Box<Expr>, u32),
    RepMinMax(Box<Expr>, u32, u32),
    Skip(Vec<String>),
    Push(Box<Expr>),
}

All possible rule expressions

Variants

Str(String)

Matches an exact string, e.g. "a"

Insens(String)

Matches an exact string, case insensitively (ASCII only), e.g. ^"a"

Range(String, String)

Matches one character in the range, e.g. 'a'..'z'

Ident(String)

Matches the rule with the given name, e.g. a

PeekSlice(i32, Option<i32>)

Matches a custom part of the stack, e.g. PEEK[..]

PosPred(Box<Expr>)

Positive lookahead; matches expression without making progress, e.g. &e

NegPred(Box<Expr>)

Negative lookahead; matches if expression doesn’t match, without making progress, e.g. !e

Seq(Box<Expr>, Box<Expr>)

Matches a sequence of two expressions, e.g. e1 ~ e2

Choice(Box<Expr>, Box<Expr>)

Matches either of two expressions, e.g. e1 | e2

Opt(Box<Expr>)

Optionally matches an expression, e.g. e?

Rep(Box<Expr>)

Matches an expression zero or more times, e.g. e*

RepOnce(Box<Expr>)

Matches an expression one or more times, e.g. e+

RepExact(Box<Expr>, u32)

Matches an expression an exact number of times, e.g. e{n}

RepMin(Box<Expr>, u32)

Matches an expression at least a number of times, e.g. e{n,}

RepMax(Box<Expr>, u32)

Matches an expression at most a number of times, e.g. e{,n}

RepMinMax(Box<Expr>, u32, u32)

Matches an expression a number of times within a range, e.g. e{m, n}

Skip(Vec<String>)

Continues to match expressions until one of the strings in the Vec is found

Push(Box<Expr>)

Matches an expression and pushes it to the stack, e.g. push(e)

Implementations

impl Expr

pub fn iter_top_down(&self) -> ExprTopDownIterator

Returns the iterator that steps the expression from top to bottom.

pub fn map_top_down<F>(self, f: F) -> Exprwhere
    F: FnMut(Expr) -> Expr,

Applies f to the expression and all its children (top to bottom).

Examples found in repository

src/optimizer/rotater.rs (line 42)

pub fn rotate(rule: Rule) -> Rule {
    fn rotate_internal(expr: Expr) -> Expr {
        match expr {
            // TODO: Use box syntax when it gets stabilized.
            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),
    }
}

src/optimizer/skipper.rs (lines 36-51)

pub fn skip(rule: Rule) -> Rule {
    fn populate_choices(expr: Expr, mut choices: Vec<String>) -> Option<Expr> {
        match expr {
            Expr::Choice(lhs, rhs) => {
                if let Expr::Str(string) = *lhs {
                    choices.push(string);
                    populate_choices(*rhs, choices)
                } else {
                    None
                }
            }
            Expr::Str(string) => {
                choices.push(string);
                Some(Expr::Skip(choices))
            }
            _ => None,
        }
    }

    let Rule { name, ty, expr } = rule;
    Rule {
        name,
        ty,
        expr: if ty == RuleType::Atomic {
            expr.map_top_down(|expr| {
                // TODO: Use box syntax when it gets stabilized.
                if let Expr::Rep(expr) = expr.clone() {
                    if let Expr::Seq(lhs, rhs) = *expr {
                        if let (Expr::NegPred(expr), Expr::Ident(ident)) = (*lhs, *rhs) {
                            if ident == "ANY" {
                                if let Some(expr) = populate_choices(*expr, vec![]) {
                                    return expr;
                                }
                            }
                        }
                    }
                };

                expr
            })
        } else {
            expr
        },
    }
}

src/optimizer/factorizer.rs (lines 17-49)

pub fn factor(rule: Rule) -> Rule {
    let Rule { name, ty, expr } = rule;
    Rule {
        name,
        ty,
        expr: expr.map_top_down(|expr| {
            // TODO: Use box syntax when it gets stabilized.
            match expr {
                Expr::Choice(lhs, rhs) => match (*lhs, *rhs) {
                    (Expr::Seq(l1, r1), Expr::Seq(l2, r2)) => {
                        if l1 == l2 {
                            Expr::Seq(l1, Box::new(Expr::Choice(r1, r2)))
                        } else {
                            Expr::Choice(Box::new(Expr::Seq(l1, r1)), Box::new(Expr::Seq(l2, r2)))
                        }
                    }
                    // Converts `(rule ~ rest) | rule` to `rule ~ rest?`, avoiding trying to match `rule` twice.
                    (Expr::Seq(l1, l2), r) => {
                        if *l1 == r {
                            Expr::Seq(l1, Box::new(Expr::Opt(l2)))
                        } else {
                            Expr::Choice(Box::new(Expr::Seq(l1, l2)), Box::new(r))
                        }
                    }
                    // Converts `rule | (rule ~ rest)` to `rule` since `(rule ~ rest)`
                    // will never match if `rule` didn't.
                    (l, Expr::Seq(r1, r2)) => {
                        if l == *r1 {
                            l
                        } else {
                            Expr::Choice(Box::new(l), Box::new(Expr::Seq(r1, r2)))
                        }
                    }
                    (lhs, rhs) => Expr::Choice(Box::new(lhs), Box::new(rhs)),
                },
                expr => expr,
            }
        }),
    }
}

pub fn map_bottom_up<F>(self, f: F) -> Exprwhere
    F: FnMut(Expr) -> Expr,

Applies f to the expression and all its children (bottom up).

Examples found in repository

src/optimizer/concatenator.rs (lines 17-31)

pub fn concatenate(rule: Rule) -> Rule {
    let Rule { name, ty, expr } = rule;
    Rule {
        name,
        ty,
        expr: expr.map_bottom_up(|expr| {
            if ty == RuleType::Atomic {
                // TODO: Use box syntax when it gets stabilized.
                match expr {
                    Expr::Seq(lhs, rhs) => match (*lhs, *rhs) {
                        (Expr::Str(lhs), Expr::Str(rhs)) => Expr::Str(lhs + &rhs),
                        (Expr::Insens(lhs), Expr::Insens(rhs)) => Expr::Insens(lhs + &rhs),
                        (lhs, rhs) => Expr::Seq(Box::new(lhs), Box::new(rhs)),
                    },
                    expr => expr,
                }
            } else {
                expr
            }
        }),
    }
}

src/optimizer/lister.rs (lines 17-40)

pub fn list(rule: Rule) -> Rule {
    let Rule { name, ty, expr } = rule;
    Rule {
        name,
        ty,
        expr: expr.map_bottom_up(|expr| {
            // TODO: Use box syntax when it gets stabilized.
            match expr {
                Expr::Seq(l, r) => match *l {
                    Expr::Rep(l) => {
                        let l = *l;
                        match l {
                            Expr::Seq(l1, l2) => {
                                // Converts `(rule ~ rest)* ~ rule` to `rule ~ (rest ~ rule)*`,
                                // avoiding matching the last `rule` twice.
                                if l1 == r {
                                    Expr::Seq(l1, Box::new(Expr::Rep(Box::new(Expr::Seq(l2, r)))))
                                } else {
                                    Expr::Seq(Box::new(Expr::Rep(Box::new(Expr::Seq(l1, l2)))), r)
                                }
                            }
                            expr => Expr::Seq(Box::new(Expr::Rep(Box::new(expr))), r),
                        }
                    }
                    expr => Expr::Seq(Box::new(expr), r),
                },
                expr => expr,
            }
        }),
    }
}

src/optimizer/unroller.rs (lines 17-64)

pub fn unroll(rule: Rule) -> Rule {
    let Rule { name, ty, expr } = rule;
    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,
        }),
    }
}

Trait Implementations

impl Clone for Expr

fn clone(&self) -> Expr

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Expr

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq<Expr> for Expr

fn eq(&self, other: &Expr) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Expr

impl StructuralEq for Expr

impl StructuralPartialEq for Expr