pj2
Class BnfParser

Object
  Utils
      Launcher
          BnfParser

public class BnfParser
extends Launcher

pj2-based parser for the BNF input language.

Nested Class Summary

static class	BnfParser.yyException thrown for irrecoverable syntax errors and stack overflow.
static interface	BnfParser.yyInput must be implemented by a scanner object to supply input to the parser.
static class	BnfParser.yyLex

Field Summary

static int	Epilog
static int	Id
protected static BnfParser	parser parser singleton.
static int	Prolog
static int	String
boolean	yyAddNull if true, null will be stored when a totally empty alternative is reduced.
protected static short[]	yyCheck parser tables.
protected static short[]	yyDefRed parser tables.
protected static short[]	yyDgoto parser tables.
static int	yyErrorCode
protected static int	yyFinal number of final state.
protected static short[]	yyGindex parser tables.
protected static short[]	yyLen parser tables.
protected static short[]	yyLhs parser tables.
protected int	yyMax initial size and increment of the state/value stack [default 256].
protected static String[]	yyNames maps symbol value to printable name.
protected static short[]	yyRindex parser tables.
protected static short[]	yySindex parser tables.
protected static short[]	yyTable parser tables.

Fields inherited from class Launcher

map, out

Fields inherited from class Utils

error

Constructor Summary

BnfParser()

Method Summary

Parser	compile(Reader in) build a parser tree from a file.
static void	main(String... args) main program.
protected Object	yybuild(BnfParser.yyInput yyLex, Object builder, String rule, Object... arg) executed whenever an alternative of a rule is reduced, called with values corresponding to Id arguments only.
protected Object	yybuild0(BnfParser.yyInput yyLex, Object builder, String rule) executed whenever an empty alternative of a rule is reduced.
protected Object	yyDefault(Object first) executed at the beginning of a reduce action.
void	yyerror(String message) simplified error message.
void	yyerror(String message, String[] expected) (syntax) error message.
protected String[]	yyExpecting(int state) computes list of expected tokens on error by tracing the tables.
Object	yyparse(BnfParser.yyInput yyLex, Object... yyarg) the generated parser.

Methods inherited from class Launcher

commands, notNull

Methods inherited from class Utils

className, error, error, error, fromString, getError, message, toChars, toString, warning, warning, warning

Methods inherited from class Object

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

Field Detail

parser

protected static final BnfParser parser

parser singleton.

yyNames

protected static final String[] yyNames

maps symbol value to printable name.

See Also:

yyExpecting(int)

Prolog

public static final int Prolog

See Also:

Constant Field Values

Id

public static final int Id

See Also:

Constant Field Values

String

public static final int String

See Also:

Constant Field Values

Epilog

public static final int Epilog

See Also:

Constant Field Values

yyErrorCode

public static final int yyErrorCode

See Also:

Constant Field Values

yyFinal

protected static final int yyFinal

number of final state.

See Also:

Constant Field Values

yyLhs

protected static final short[] yyLhs

parser tables. Order is mandated by jay.

yyLen

protected static final short[] yyLen

parser tables. Order is mandated by jay.

yyDefRed

protected static final short[] yyDefRed

parser tables. Order is mandated by jay.

yyDgoto

protected static final short[] yyDgoto

parser tables. Order is mandated by jay.

yySindex

protected static final short[] yySindex

parser tables. Order is mandated by jay.

yyRindex

protected static final short[] yyRindex

parser tables. Order is mandated by jay.

yyGindex

protected static final short[] yyGindex

parser tables. Order is mandated by jay.

yyTable

protected static final short[] yyTable

parser tables. Order is mandated by jay.

yyCheck

protected static final short[] yyCheck

parser tables. Order is mandated by jay.

yyMax

protected int yyMax

initial size and increment of the state/value stack [default 256]. This is not final so that it can be overwritten outside of invocations of yyparse(pj2.BnfParser.yyInput, java.lang.Object...).

yyAddNull

public boolean yyAddNull

if true, null will be stored when a totally empty alternative is reduced.

Constructor Detail

BnfParser

public BnfParser()

Method Detail

main

public static void main(String... args)
                 throws ClassNotFoundException,
                        IOException

main program.

Throws:

ClassNotFoundException

IOException

compile

public Parser compile(Reader in)
               throws IOException

build a parser tree from a file.

Specified by:

compile in class Launcher

Returns:

null on error.

Throws:

IOException

yyerror

public void yyerror(String message)

simplified error message.

See Also:

yyerror(java.lang.String, java.lang.String[])

yyerror

public void yyerror(String message,
                    String[] expected)

(syntax) error message. Can be overwritten to control message format.

Parameters:

message - text to be displayed.

expected - list of acceptable tokens, if available.

yyExpecting

protected String[] yyExpecting(int state)

computes list of expected tokens on error by tracing the tables.

Parameters:

state - for which to compute the list.

Returns:

list of token names.

yyDefault

protected Object yyDefault(Object first)

executed at the beginning of a reduce action. Used as $$ = yyDefault($1), prior to the user-specified action, if any. Can be overwritten to provide deep copy, etc.

Parameters:

first - value for $1, or null.

Returns:

first.

yyparse

public Object yyparse(BnfParser.yyInput yyLex,
                      Object... yyarg)
               throws IOException,
                      BnfParser.yyException

the generated parser. Maintains a dynamic state and value stack.

Parameters:

yyLex - scanner.

yyarg - [0] debug message writer implementing yyDebug, and/or tree builder for yybuild().

Returns:

result of the last reduction, if any.

Throws:

BnfParser.yyException - on irrecoverable parse error.

IOException

yybuild0

protected Object yybuild0(BnfParser.yyInput yyLex,
                          Object builder,
                          String rule)

executed whenever an empty alternative of a rule is reduced. If yyAddNull is true, sends null to yybuild(pj2.BnfParser.yyInput, java.lang.Object, java.lang.String, java.lang.Object...).

yybuild

protected Object yybuild(BnfParser.yyInput yyLex,
                         Object builder,
                         String rule,
                         Object... arg)

executed whenever an alternative of a rule is reduced, called with values corresponding to Id arguments only. ArrayList arguments are flattened, others are not.

Silently filter by invoking builder.rulename(int,List) or builder.rulename(List), if either, with the current scanner position and the flattened argument list.

Returns:

result value from builder or flattened argument list.