org.stekikun.dolmen.unparam

Class Grammars

java.lang.Object

org.stekikun.dolmen.unparam.Grammars

public abstract class Grammars
extends Object

Static utilities about Grammars

Author:

Stéphane Lescuyer

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Grammars.Dependencies Represents the dependencies between the various non-terminals in some grammar.
static class	Grammars.NTermsInfo Gathers the result of the computation of the NULLABLE, FIRST and FOLLOW sets on non-terminals in a given grammar
static class	Grammars.PredictionTable Instances of this class hold a prediction table for some grammar.

Method Summary

Modifier and Type	Method and Description
static Grammars.NTermsInfo	analyseGrammar(Grammar grammar, @Nullable Grammars.Dependencies deps_, @Nullable Reporter reporter) Analyze the given grammar and compute for every non-terminal whether it is nullable, and the associated FIRST and FOLLOW sets.
static Grammars.Dependencies	dependencies(Grammar grammar) Computes the map of dependencies between the non-terminals of the given grammar, i.e. associates to every non-terminal in grammar the set of non-terminals which appear in the right-hand side of productions for this non-terminal.
protected static Map<String,Set<String>>	first(Grammars.Dependencies deps, Grammar grammar, Set<String> nullable)
protected static Map<String,Set<String>>	follow(Grammars.Dependencies deps, Grammar grammar, Set<String> nullable, Map<String,Set<String>> first)
protected static Set<String>	nullable(Grammars.Dependencies deps, Grammar grammar) NB: In all generality this is only a correct approximation, so non-terminals which are not in the resulting state are not guaranteed to always produce non-empty matches.
static Grammars.PredictionTable	predictionTable(Grammar grammar, Grammars.NTermsInfo infos) Constructs a prediction table for the given grammar.

Methods inherited from class java.lang.Object

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

Method Detail

dependencies

public static Grammars.Dependencies dependencies(Grammar grammar)

Computes the map of dependencies between the non-terminals of the given grammar, i.e. associates to every non-terminal in grammar the set of non-terminals which appear in the right-hand side of productions for this non-terminal.

Parameters:

grammar -

Returns:

the map of dependencies

nullable

protected static Set<String> nullable(Grammars.Dependencies deps,
                                      Grammar grammar)

NB: In all generality this is only a correct approximation, so non-terminals which are not in the resulting state are not guaranteed to always produce non-empty matches.

Parameters:

deps -

grammar -

Returns:

the set of non-terminals in grammar which can produce empty sequence of tokens

first

protected static Map<String,Set<String>> first(Grammars.Dependencies deps,
                                               Grammar grammar,
                                               Set<String> nullable)

follow

protected static Map<String,Set<String>> follow(Grammars.Dependencies deps,
                                                Grammar grammar,
                                                Set<String> nullable,
                                                Map<String,Set<String>> first)

analyseGrammar

public static Grammars.NTermsInfo analyseGrammar(Grammar grammar,
                                                 @Nullable Grammars.Dependencies deps_,
                                                 @Nullable Reporter reporter)

Analyze the given grammar and compute for every non-terminal whether it is nullable, and the associated FIRST and FOLLOW sets. If reporter is non-null, this also returns potentially unused symbols discovered during the analysis of the grammar.

Parameters:

grammar -

deps_ - null, or dependencies already computed for the given grammar

reporter - an instance to report problems to, or null if no problem report is desired

Returns:

the results of the analysis

predictionTable

public static Grammars.PredictionTable predictionTable(Grammar grammar,
                                                       Grammars.NTermsInfo infos)

Constructs a prediction table for the given grammar. The nullable, first and follow sets for the grammar's non-terminals must be provided in infos.

Parameters:

grammar -

infos -

Returns:

the prediction table computed for grammar