Class EarleyGenerator

A specialized version of the Earley parser that generates all possible sentences from a grammar.

Inheritance
object
EarleyParser
EarleyGenerator
Inherited Members
Namespace: EarleyParser
Assembly: EarleyParser.dll
Syntax
public class EarleyGenerator : EarleyParser
Remarks

Instead of parsing a specific input, it builds the complete parse forest for all possible sentences up to a specified length.

Key features:

  1. Complete Parse Forest Generation:
    • Generates all possible parse trees for sentences up to maxWords length
    • Maintains the same chart structure as the parser for consistency
    • Uses "generator" tokens as placeholders for actual input
  2. Generation Modes:
    • Parts of Speech Sequences: Generate sequences of grammatical categories
    • Full Parse Trees: Generate complete bracketed parse tree representations
  3. Analysis Capabilities:
    • Counts total number of possible derivations
    • Analyzes tree properties (recursion, basic trees)
    • Supports both context-free and linear indexed grammars

This class is particularly useful for:

  • Grammar analysis and validation
  • Testing grammar coverage
  • Generating training data
  • Understanding grammar ambiguity

Constructors

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EarleyGenerator(Grammar, Vocabulary, int)

Initializes a new instance of the EarleyGenerator class.

Declaration
public EarleyGenerator(Grammar g, Vocabulary v, int maxWords)
Parameters
Type Name Description
Grammar g

The grammar to use for generation.
Vocabulary v

The vocabulary that maps words to their possible parts of speech.
int maxWords

The maximum length of sentences to generate.

Methods

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AddLexicalizedRules(List<Rule>, int, bool)

Skips lexicalized rules processing in generation mode.

Declaration
protected override void AddLexicalizedRules(List<Rule> lexicalRules, int i, bool preprocess = true)
Parameters
Type Name Description
List<Rule> lexicalRules

Not used in generator mode.
int i

Not used in generator mode.
bool preprocess

Not used in generator mode.
Overrides
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GetAllSequences(bool)

Gets all possible sequences that can be generated from the grammar.

Declaration
public string[][] GetAllSequences(bool onlyPartsOfSpeechSequences = true)
Parameters
Type Name Description
bool onlyPartsOfSpeechSequences

If true, returns only sequences of parts of speech. If false, returns full bracketed parse trees.
Returns
Type Description
string[][]

A two-dimensional array of sequences, where each row represents a different length.
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GetPossibleSyntacticCategoriesForToken(string)

Gets all possible syntactic categories for a token in generation mode.

Declaration
protected override HashSet<string> GetPossibleSyntacticCategoriesForToken(string nextScannableTerm)
Parameters
Type Name Description
string nextScannableTerm

Not used in generator mode.
Returns
Type Description
HashSet<string>

A set of all possible syntactic categories from the vocabulary.
Overrides
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PrepareEarleyTable(string[], int)

Prepares the Earley table for sentence generation.

Declaration
protected override EarleyColumn[] PrepareEarleyTable(string[] text, int maxWords)
Parameters
Type Name Description
string[] text

Not used in generator mode.
int maxWords

The maximum length of sentences to generate.
Returns
Type Description
EarleyColumn[]

An array of EarleyColumn objects representing the generation table.
Overrides