java_cup

Class non_terminal

java.lang.Object

java_cup.symbol

java_cup.non_terminal

public class non_terminal
extends symbol

This class represents a non-terminal symbol in the grammar. Each non terminal has a textual name, an index, and a string which indicates the type of object it will be implemented with at runtime (i.e. the class of object that will be pushed on the parse stack to represent it).

Version:

last updated: 11/25/95

Author:

Scott Hudson

Field Summary

Fields

Modifier and Type	Field and Description
protected static Hashtable	_all Table of all non-terminals -- elements are stored using name strings as the key
protected terminal_set	_first_set First set for this non-terminal.
protected boolean	_nullable Nullability of this non terminal.
protected Hashtable	_productions Table of all productions with this non terminal on the LHS.
protected static int	next_index Static counter to assign unique indexes.
protected static int	next_nt Static counter for creating unique non-terminal names
static non_terminal	START_nt special non-terminal for start symbol

Fields inherited from class java_cup.symbol

_index, _name, _stack_type, _use_count

Constructor Summary

Constructors

Constructor and Description
non_terminal(String nm) Constructor with default type.
non_terminal(String nm, String tp) Full constructor.

Method Summary

Methods

Modifier and Type	Method and Description
void	add_production(production prod) Add a production to our set of productions.
static Enumeration	all() Access to all non-terminals.
static void	compute_first_sets() Compute first sets for all non-terminals.
static void	compute_nullability() Compute nullability of all non-terminals.
static non_terminal	find(String with_name) lookup a non terminal by name string
terminal_set	first_set() First set for this non-terminal.
boolean	is_non_term() Indicate that this symbol is a non-terminal.
protected boolean	looks_nullable() Test to see if this non terminal currently looks nullable.
boolean	nullable() Nullability of this non terminal.
int	num_productions() Total number of productions with this non terminal on the LHS.
static int	number() Total number of non-terminals.
Enumeration	productions() Access to productions with this non terminal on the LHS.
String	toString() convert to string

Methods inherited from class java_cup.symbol

index, name, note_use, stack_type, use_count

Methods inherited from class java.lang.Object

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

Field Detail

_all

protected static Hashtable _all

Table of all non-terminals -- elements are stored using name strings as the key

next_index

protected static int next_index

Static counter to assign unique indexes.

next_nt

protected static int next_nt

Static counter for creating unique non-terminal names

START_nt

public static final non_terminal START_nt

special non-terminal for start symbol

_productions

protected Hashtable _productions

Table of all productions with this non terminal on the LHS.

_nullable

protected boolean _nullable

Nullability of this non terminal.

_first_set

protected terminal_set _first_set

First set for this non-terminal.

Constructor Detail

non_terminal

public non_terminal(String nm,
            String tp)

Full constructor.

Parameters:

nm - the name of the non terminal.

tp - the type string for the non terminal.

non_terminal

public non_terminal(String nm)

Constructor with default type.

Parameters:

nm - the name of the non terminal.

Method Detail

all

public static Enumeration all()

Access to all non-terminals.

find

public static non_terminal find(String with_name)

lookup a non terminal by name string

number

public static int number()

Total number of non-terminals.

compute_nullability

public static void compute_nullability()
                                throws internal_error

Compute nullability of all non-terminals.

Throws:

internal_error

compute_first_sets

public static void compute_first_sets()
                               throws internal_error

Compute first sets for all non-terminals. This assumes nullability has already computed.

Throws:

internal_error

productions

public Enumeration productions()

Access to productions with this non terminal on the LHS.

num_productions

public int num_productions()

Total number of productions with this non terminal on the LHS.

add_production

public void add_production(production prod)
                    throws internal_error

Add a production to our set of productions.

Throws:

internal_error

nullable

public boolean nullable()

Nullability of this non terminal.

first_set

public terminal_set first_set()

First set for this non-terminal.

is_non_term

public boolean is_non_term()

Indicate that this symbol is a non-terminal.

Specified by:

is_non_term in class symbol

looks_nullable

protected boolean looks_nullable()
                          throws internal_error

Test to see if this non terminal currently looks nullable.

Throws:

internal_error

toString

public String toString()

convert to string

Overrides:

toString in class symbol