step3
Class screen

java.lang.Object
  step3.screen

public class screen
extends Object

lexical analysis for lines with closed if statements and arithmetic expressions with identifiers. Note: screening single-quoted string literals is more efficient.

Nested Class Summary

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

Field Summary

static int	_else
static int	_fi
static int	_if
static int	_then
static int	Id
static int	Number
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.

Constructor Summary

screen()

Method Summary

static void	main(String[] args) main program to test parser.
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(screen.yyInput yyLex) the generated parser.
Object	yyparse(screen.yyInput yyLex, Object yydebug) the generated parser, with debugging messages.

Methods inherited from class java.lang.Object

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

Field Detail

Id

public static final int Id

See Also:

Constant Field Values

Number

public static final int Number

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Constant Field Values

_else

public static final int _else

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Constant Field Values

_fi

public static final int _fi

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Constant Field Values

_if

public static final int _if

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Constant Field Values

_then

public static final int _then

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Constant Field Values

yyErrorCode

public static final int yyErrorCode

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Constant Field Values

yyFinal

protected static final int yyFinal

number of final state.

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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.

yyNames

protected static final String[] yyNames

maps symbol value to printable name.

See Also:

yyExpecting(int)

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(step3.screen.yyInput, java.lang.Object).

Constructor Detail

screen

public screen()

Method Detail

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.

yyparse

public Object yyparse(screen.yyInput yyLex,
                      Object yydebug)
               throws IOException,
                      screen.yyException

the generated parser, with debugging messages. Maintains a dynamic state and value stack.

Parameters:

yyLex - scanner.

yydebug - debug message writer implementing yyDebug, or null.

Returns:

result of the last reduction, if any.

Throws:

screen.yyException - on irrecoverable parse error.

IOException

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(screen.yyInput yyLex)
               throws IOException,
                      screen.yyException

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

Parameters:

yyLex - scanner.

Returns:

result of the last reduction, if any.

Throws:

screen.yyException - on irrecoverable parse error.

IOException

main

public static void main(String[] args)
                 throws screen.yyException,
                        IOException

main program to test parser. static scanner.

Throws:

screen.yyException

IOException