Package jjparse.description

Class Description

java.lang.Object

jjparse.description.Description

Direct Known Subclasses:

Choice, Empty, Literal, Negation, RegExp, Sequence

public abstract sealed class Description
extends Object
permits Choice, Literal, Negation, RegExp, Sequence, Empty

The base class for all kinds of Parsing.Parser Descriptions.

A Description describes the expectation of a Parsing.Parser and can be used to generate more informative error messages in case of a Parsing.Failure. The following kinds of Descriptions are supported:

• Literal: A Description describing that a specific String literal was expected.
• RegExp: A Description describing that a specific Pattern was expected.
• Choice: A Description that represents a choice between other Descriptions.
• Sequence: A Description that represents a sequence of other Descriptions.
• Negation: A Description that negates another Description.
• Empty: An empty Description that does not provide further information.

Author:

Björn Lötters

See Also:

• Choice
• Literal
• Negation
• RegExp
• Sequence
• Empty
• Parsing.Parser
• Parsing.Parser.description()

Constructor Summary

Constructors

Constructor	Description
Description()	Construct a new Description.

Method Summary

Modifier and Type	Method	Description
final Description	and(Description description)	Creates a new Description by creating a Sequence from this and the provided Description.
abstract Optional<String>	describe()	Produces a String that explains what a corresponding Parsing.Parser would expect according to this Description.
final Description	negate()	Creates a new Description by creating a Negation from this Description.
final Description	normalize()	Normalizes this Description such that Negations are propagated downwards to the individual Literal and RegExp Descriptions.
final Description	or(Description alternative)	Creates a new Description by creating a Choice from this and the provided Description.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

Description

public Description()

Construct a new Description.

Method Details

describe

public abstract Optional<String> describe()

Produces a String that explains what a corresponding Parsing.Parser would expect according to this Description.

Returns:

An Optional String where Optional.empty() is returned in case this Description is Empty.

normalize

public final Description normalize()

Normalizes this Description such that Negations are propagated downwards to the individual Literal and RegExp Descriptions. Moreover, Choices of RegExps are summarized into a single RegExp.

Returns:

The normalized Description.

and

public final Description and(Description description)

Creates a new Description by creating a Sequence from this and the provided Description.

Parameters:

description - The second Description.

Returns:

A Sequence Description containing this and the provided Description in this order.

or

public final Description or(Description alternative)

Creates a new Description by creating a Choice from this and the provided Description.

Parameters:

alternative - The alternative Description.

Returns:

A Choice Description containing this and the provided Description in this order.

negate

public final Description negate()

Creates a new Description by creating a Negation from this Description.

Returns:

A Negation of this Description.