# [−] [src] Struct regex_syntax::hir::Hir

    pub struct Hir { /* fields omitted */ }

A high-level intermediate representation (HIR) for a regular expression.

The HIR of a regular expression represents an intermediate step between its abstract syntax (a structured description of the concrete syntax) and compiled byte codes. The purpose of HIR is to make regular expressions easier to analyze. In particular, the AST is much more complex than the HIR. For example, while an AST supports arbitrarily nested character classes, the HIR will flatten all nested classes into a single set. The HIR will also "compile away" every flag present in the concrete syntax. For example, users of HIR expressions never need to worry about case folding; it is handled automatically by the translator (e.g., by translating `(?i)A` to `[aA]`).

If the HIR was produced by a translator that disallows invalid UTF-8, then the HIR is guaranteed to match UTF-8 exclusively.

This type defines its own destructor that uses constant stack space and heap space proportional to the size of the HIR.

The specific type of an HIR expression can be accessed via its `kind` or `into_kind` methods. This extra level of indirection exists for two reasons:

1. Construction of an HIR expression must use the constructor methods on this `Hir` type instead of building the `HirKind` values directly. This permits construction to enforce invariants like "concatenations always consist of two or more sub-expressions."
2. Every HIR expression contains attributes that are defined inductively, and can be computed cheaply during the construction process. For example, one such attribute is whether the expression must match at the beginning of the text.

Also, an `Hir`'s `fmt::Display` implementation prints an HIR as a regular expression pattern string, and uses constant stack space and heap space proportional to the size of the `Hir`.

## Methods

### `impl Hir` [src]

#### `pub fn kind(&self) -> &HirKind` [src]

Returns a reference to the underlying HIR kind.

#### `pub fn into_kind(self) -> HirKind` [src]

Consumes ownership of this HIR expression and returns its underlying `HirKind`.

#### `pub fn empty() -> Hir` [src]

Returns an empty HIR expression.

An empty HIR expression always matches, including the empty string.

#### `pub fn literal(lit: Literal) -> Hir` [src]

Creates a literal HIR expression.

If the given literal has a `Byte` variant with an ASCII byte, then this method panics. This enforces the invariant that `Byte` variants are only used to express matching of invalid UTF-8.

#### `pub fn class(class: Class) -> Hir` [src]

Creates a class HIR expression.

#### `pub fn anchor(anchor: Anchor) -> Hir` [src]

Creates an anchor assertion HIR expression.

#### `pub fn word_boundary(word_boundary: WordBoundary) -> Hir` [src]

Creates a word boundary assertion HIR expression.

#### `pub fn repetition(rep: Repetition) -> Hir` [src]

Creates a repetition HIR expression.

#### `pub fn group(group: Group) -> Hir` [src]

Creates a group HIR expression.

#### `pub fn concat(exprs: Vec<Hir>) -> Hir` [src]

Returns the concatenation of the given expressions.

This flattens the concatenation as appropriate.

#### `pub fn alternation(exprs: Vec<Hir>) -> Hir` [src]

Returns the alternation of the given expressions.

This flattens the alternation as appropriate.

#### `pub fn dot(bytes: bool) -> Hir` [src]

Build an HIR expression for `.`.

A `.` expression matches any character except for `\n`. To build an expression that matches any character, including `\n`, use the `any` method.

If `bytes` is `true`, then this assumes characters are limited to a single byte.

#### `pub fn any(bytes: bool) -> Hir` [src]

Build an HIR expression for `(?s).`.

A `(?s).` expression matches any character, including `\n`. To build an expression that matches any character except for `\n`, then use the `dot` method.

If `bytes` is `true`, then this assumes characters are limited to a single byte.

#### `pub fn is_always_utf8(&self) -> bool` [src]

Return true if and only if this HIR will always match valid UTF-8.

When this returns false, then it is possible for this HIR expression to match invalid UTF-8.

#### `pub fn is_all_assertions(&self) -> bool` [src]

Returns true if and only if this entire HIR expression is made up of zero-width assertions.

This includes expressions like `^$\b\A\z` and even `((\b)+())*^`, but not `^a`.

#### `pub fn is_anchored_start(&self) -> bool` [src]

Return true if and only if this HIR is required to match from the beginning of text. This includes expressions like `^foo`, `^(foo|bar)`, `^foo|^bar` but not `^foo|bar`.

#### `pub fn is_anchored_end(&self) -> bool` [src]

Return true if and only if this HIR is required to match at the end of text. This includes expressions like `foo$`, `(foo|bar)$`, `foo$|bar$` but not `foo$|bar`.

#### `pub fn is_line_anchored_start(&self) -> bool` [src]

Return true if and only if this HIR is required to match from the beginning of text or the beginning of a line. This includes expressions like `^foo`, `(?m)^foo`, `^(foo|bar)`, `^(foo|bar)`, `(?m)^foo|^bar` but not `^foo|bar` or `(?m)^foo|bar`.

Note that if `is_anchored_start` is `true`, then `is_line_anchored_start` will also be `true`. The reverse implication is not true. For example, `(?m)^foo` is line anchored, but not `is_anchored_start`.

#### `pub fn is_line_anchored_end(&self) -> bool` [src]

Return true if and only if this HIR is required to match at the end of text or the end of a line. This includes expressions like `foo$`, `(?m)foo$`, `(foo|bar)$`, `(?m)(foo|bar)$`, `foo$|bar$`, `(?m)(foo|bar)$`, but not `foo$|bar` or `(?m)foo$|bar`.

Note that if `is_anchored_end` is `true`, then `is_line_anchored_end` will also be `true`. The reverse implication is not true. For example, `(?m)foo$` is line anchored, but not `is_anchored_end`.

#### `pub fn is_any_anchored_start(&self) -> bool` [src]

Return true if and only if this HIR contains any sub-expression that is required to match at the beginning of text. Specifically, this returns true if the `^` symbol (when multiline mode is disabled) or the `\A` escape appear anywhere in the regex.

#### `pub fn is_any_anchored_end(&self) -> bool` [src]

Return true if and only if this HIR contains any sub-expression that is required to match at the end of text. Specifically, this returns true if the `$` symbol (when multiline mode is disabled) or the `\z` escape appear anywhere in the regex.

#### `pub fn is_match_empty(&self) -> bool` [src]

Return true if and only if the empty string is part of the language matched by this regular expression.

This includes `a*`, `a?b*`, `a{0}`, `()`, `()+`, `^$`, `a|b?`, `\B`, but not `a`, `a+` or `\b`.

#### `pub fn is_literal(&self) -> bool` [src]

Return true if and only if this HIR is a simple literal. This is only true when this HIR expression is either itself a `Literal` or a concatenation of only `Literal`s.

For example, `f` and `foo` are literals, but `f+`, `(foo)`, `foo()` are not (even though that contain sub-expressions that are literals).

#### `pub fn is_alternation_literal(&self) -> bool` [src]

Return true if and only if this HIR is either a simple literal or an alternation of simple literals. This is only true when this HIR expression is either itself a `Literal` or a concatenation of only `Literal`s or an alternation of only `Literal`s.

For example, `f`, `foo`, `a|b|c`, and `foo|bar|baz` are alternaiton literals, but `f+`, `(foo)`, `foo()` are not (even though that contain sub-expressions that are literals).

## Trait Implementations

### `impl PartialEq<Hir> for Hir` [src]

#### `fn eq(&self, other: &Hir) -> bool` [src]

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

#### `fn ne(&self, other: &Hir) -> bool` [src]

This method tests for `!=`.

### `impl Clone for Hir` [src]

#### `fn clone(&self) -> Hir` [src]

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`1.0.0 [src]

Performs copy-assignment from `source`. Read more

### `impl Eq for Hir` [src]

### `impl Drop for Hir` [src]

A custom `Drop` impl is used for `HirKind` such that it uses constant stack space but heap space proportional to the depth of the total `Hir`.

#### `fn drop(&mut self)` [src]

Executes the destructor for this type. Read more

### `impl Display for Hir` [src]

Print a display representation of this Hir.

The result of this is a valid regular expression pattern string.

This implementation uses constant stack space and heap space proportional to the size of the `Hir`.

#### `fn fmt(&self, f: &mut Formatter) -> Result` [src]

Formats the value using the given formatter. Read more

### `impl Debug for Hir` [src]

#### `fn fmt(&self, f: &mut Formatter) -> Result` [src]

Formats the value using the given formatter. Read more

## Auto Trait Implementations

### `impl Send for Hir`

### `impl Sync for Hir`

## Blanket Implementations

### `impl<T> From<T> for T` [src]

#### `fn from(t: T) -> T` [src]

Performs the conversion.

### `impl<T> ToOwned for T where
T: Clone,` [src]

#### `type Owned = T`

The resulting type after obtaining ownership.

#### `fn to_owned(&self) -> T` [src]

Creates owned data from borrowed data, usually by cloning. Read more

#### `fn clone_into(&self, target: &mut T)` [src]

🔬 This is a nightly-only experimental API. (`toowned_clone_into`)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

### `impl<T> ToString for T where
T: Display + ?Sized,` [src]

#### `default fn to_string(&self) -> String` [src]

Converts the given value to a `String`. Read more

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `fn into(self) -> U` [src]

Performs the conversion.

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>` [src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>` [src]

Performs the conversion.

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `fn borrow_mut(&mut self) -> &mut T` [src]

Mutably borrows from an owned value. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `fn borrow(&self) -> &T` [src]

Immutably borrows from an owned value. Read more

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&self) -> TypeId` [src]

Gets the `TypeId` of `self`. Read more

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