Module feature 

The grammar feature union forms (docs/grammar/feature-union.md).

One table describes every expression kind, every operation of the scanner and action language and every grammar declaration the feature union adds, and the native listing, links and JSON codecs read and write them from that table, so the serializations stay in step with each other and with js/src/grammar-feature-forms.js.

Structs

FeatureForm

One feature expression form or one operation: a head word and its field values, in the order of FEATURE_EXPRESSION_FORMS or OPERATION_FORMS.

GrammarDeclarations

The grammar-level declarations of the feature union.

GrammarMacro

A macro declaration: macro NAME(P, ...) = EXPRESSION.

GrammarScanner

An external scanner declaration.

RuleAttributes

The optional parts of a rule the feature union adds.

Enums

ByteClassItem

One item of a byte class.

FeatureExpr

An expression of the grammar feature union.

FieldType

The type of one field of a feature form or an operation.

FieldValue

The value of one field of a feature form or an operation.

OperationCategory

Whether an operation is a statement, a condition or a value.

PrecedenceEntry

One entry of a precedence order: a named precedence or a rule, whose productions it ranks.

UnicodeClassItem

One item of a character class that names Unicode properties.

Constants

FEATURE_EXPRESSION_FORMS

The expression kinds the feature union adds, with their fields in listing order.

MATCHING_MODES

The ways a grammar may match: generalized (every alternative), PEG (first and greedy) or longest (generalized, ties going to the longer token).

MAX_INTEGER_DIGITS

The longest integer a form may spell, in decimal digits.

OPERATION_FORMS

The operation language of external scanners, semantic actions and predicates, with each operation’s category and fields in listing order.

SETTLING_STEPS

The steps that settle two parses of one text that end alike, as a grammar’s (settling STEP ...) declares them.

Functions

check_integer

Checks the text of an integer field: an optional - and at most 15 digits.

class_expression

A character class: a plain GrammarExpr::CharClass when every item is a character or a range, otherwise a FeatureExpr::UnicodeClass.

default_settling

The settling of a grammar that declares none, by its matching.

feature_expression_fields

The fields of the feature expression form head, when it is one.

operation_form

The category and fields of the operation head, when it is one.

settling_problem

Why steps is no settling, or None: every step is known and given once, and exactly the last one settles a tie.

Type Aliases

FormFields

The fields of one form, as (key, type) pairs in listing order.

Operation

One operation of the scanner and action language.