Struct regex_syntax::hir::Hir
[−]
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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:
- Construction of an HIR expression must use the constructor methods
on this
Hir
type instead of building theHirKind
values directly. This permits construction to enforce invariants like "concatenations always consist of two or more sub-expressions." - 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
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pub fn kind(&self) -> &HirKind
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Returns a reference to the underlying HIR kind.
pub fn into_kind(self) -> HirKind
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Consumes ownership of this HIR expression and returns its underlying
HirKind
.
pub fn empty() -> Hir
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Returns an empty HIR expression.
An empty HIR expression always matches, including the empty string.
pub fn literal(lit: Literal) -> Hir
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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
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Creates a class HIR expression.
pub fn anchor(anchor: Anchor) -> Hir
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Creates an anchor assertion HIR expression.
pub fn word_boundary(word_boundary: WordBoundary) -> Hir
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Creates a word boundary assertion HIR expression.
pub fn repetition(rep: Repetition) -> Hir
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Creates a repetition HIR expression.
pub fn group(group: Group) -> Hir
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Creates a group HIR expression.
pub fn concat(exprs: Vec<Hir>) -> Hir
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Returns the concatenation of the given expressions.
This flattens the concatenation as appropriate.
pub fn alternation(exprs: Vec<Hir>) -> Hir
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Returns the alternation of the given expressions.
This flattens the alternation as appropriate.
pub fn dot(bytes: bool) -> Hir
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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
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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
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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
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Returns true if and only if this entire HIR expression is made up of zero-width assertions.
This includes expressions like ^$\b\A\z
and even ((\b)+())*^
, but
not ^a
.
pub fn is_anchored_start(&self) -> bool
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Return true if and only if this HIR is required to match from the
beginning of text. This includes expressions like ^foo
, ^(foo|bar)
,
^foo|^bar
but not ^foo|bar
.
pub fn is_anchored_end(&self) -> bool
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Return true if and only if this HIR is required to match at the end
of text. This includes expressions like foo$
, (foo|bar)$
,
foo$|bar$
but not foo$|bar
.
pub fn is_any_anchored_start(&self) -> bool
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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
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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
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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
.
Trait Implementations
impl Clone for Hir
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fn clone(&self) -> Hir
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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 Debug for Hir
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fn fmt(&self, __arg_0: &mut Formatter) -> Result
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Formats the value using the given formatter. Read more
impl Eq for Hir
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impl PartialEq for Hir
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fn eq(&self, __arg_0: &Hir) -> bool
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This method tests for self
and other
values to be equal, and is used by ==
. Read more
fn ne(&self, __arg_0: &Hir) -> bool
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This method tests for !=
.
impl Display for Hir
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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
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Formats the value using the given formatter. Read more
impl Drop for Hir
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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
.