Grammar Struct Reference

Public Member Functions
	Grammar (std::string filename)
	Constructs a grammar by reading from the specified file.
void	ReadFromFile ()
	Reads and loads the grammar from a file.
void	AddRule (const std::string &antecedent, const std::string &consequent)
	Adds a rule to the grammar.
void	SetAxiom (const std::string &axiom)
	Sets the axiom (entry point) of the grammar.
bool	HasEmptyProduction (const std::string &antecedent)
	Checks if a given antecedent has an empty production.
std::vector< std::pair< const std::string, production > >	FilterRulesByConsequent (const std::string &arg)
	Filters grammar rules that contain a specific token in their consequent.
void	Debug ()
	Prints the current grammar structure to standard output.

Static Public Member Functions
static std::vector< std::string >	Split (const std::string &s)
	Splits a production string into individual tokens.
static bool	HasLeftRecursion (const std::string &antecedent, const std::vector< std::string > &consequent)
	Checks if a rule exhibits left recursion.

Public Attributes
std::unordered_map< std::string, std::vector< production > >	g_
	Stores the grammar rules with each antecedent mapped to a list of productions.
std::string	axiom_
	The axiom or entry point of the grammar.
const std::string	kFilename
	The filename from which the grammar is read.

Constructor & Destructor Documentation

Grammar()

Grammar::Grammar ( std::string filename )

explicit

Constructs a grammar by reading from the specified file.

Parameters

filename

Path to the file containing the grammar definitions.

Initializes the grammar by setting the filename for input. The actual grammar data is read and processed through the read_from_file function.

Member Function Documentation

AddRule()

void Grammar::AddRule	(	const std::string &	antecedent,
		const std::string &	consequent )

Adds a rule to the grammar.

Parameters

antecedent	The left-hand side (LHS) symbol of the rule.
consequent	The right-hand side (RHS) of the rule as a string.

Adds a rule to the grammar by specifying the antecedent symbol and the consequent production. This function processes and adds each rule for parsing.

Debug()

void Grammar::Debug

(

)

Prints the current grammar structure to standard output.

This function provides a debug view of the grammar by printing out all rules, the axiom, and other relevant details.

FilterRulesByConsequent()

std::vector< std::pair< const std::string, production > > Grammar::FilterRulesByConsequent

(

const std::string &

arg

)

Filters grammar rules that contain a specific token in their consequent.

Parameters

arg	The token to search for within the consequents of the rules.

Returns

std::vector of pairs where each pair contains an antecedent and its respective production that includes the specified token.

Searches for rules in which the specified token is part of the consequent and returns those rules.

HasEmptyProduction()

bool Grammar::HasEmptyProduction

(

const std::string &

antecedent

)

Checks if a given antecedent has an empty production.

Parameters

antecedent

The left-hand side (LHS) symbol to check.

Returns

true if there exists an empty production for the antecedent, otherwise false.

An empty production is represented as <antecedent> -> ;, indicating that the antecedent can produce an empty string.

HasLeftRecursion()

bool Grammar::HasLeftRecursion ( const std::string & antecedent, const std::vector< std::string > & consequent )

static

Checks if a rule exhibits left recursion.

Parameters

antecedent	The left-hand side (LHS) symbol of the rule.
consequent	The right-hand side (RHS) vector of tokens of the rule.

Returns

true if the rule has left recursion (e.g., A -> A + A), otherwise false.

Left recursion is identified when the antecedent of a rule appears as the first symbol in its consequent, which may cause issues in top-down parsing algorithms.

ReadFromFile()

void Grammar::ReadFromFile

(

)

Reads and loads the grammar from a file.

This function reads the grammar rules from the specified file, parsing each rule and storing it in the grammar structure. The file format requirements are outlined in the README.md.

Exceptions

GrammarError

if there are errors reading symbols, parsing the grammar, or splitting the rules as specified in the input file.

SetAxiom()

void Grammar::SetAxiom

(

const std::string &

axiom

)

Sets the axiom (entry point) of the grammar.

Parameters

axiom

The entry point or start symbol of the grammar.

Defines the starting point for the grammar, which is used in parsing algorithms and must be a non-terminal symbol present in the grammar.

Split()

std::vector< std::string > Grammar::Split ( const std::string & s )

static

Splits a production string into individual tokens.

Parameters

s	The production string to split.

Returns

std::vector containing tokens extracted from the production string.

The function decomposes a production string into individual symbols based on the symbol table, allowing terminals and non-terminals to be identified.

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The documentation for this struct was generated from the following files:

• include/grammar.hpp
• src/grammar.cpp