org.colos.ejs.library.control.value
Class ParserSuryono

java.lang.Object
  org.colos.ejs.library.control.value.ParserSuryono

public final class ParserSuryono
extends java.lang.Object

The class Parser is a mathematical expression parser.

Example of code that uses this class:

 Parser parser = new Parser(1);    // creates parser with one variable
 parser.defineVariable(0,"x");     // lets the variable be 'x'
 parser.define("Math.sin(x)/x");        // defines function: sin(x)/x
 parser.parse();                   // parses the function

 IMPORTANT: Notice that my variables start at 0 in this version


 // calculates: sin(x)/x with x = -5.0 .. +5.0 in 20 steps
 // and prints the result to standard output.

 double result;
 for (i=-10; i <= 10; i++) {
   parser.setVariable(0,(double)i/2.0f);
   result = parser.evaluate();
   System.out.println(result);
 }
 

Field Summary

static int	CODE_DAMAGED Code damaged.
static int	COMMA_EXPECTED Comma expected.
static int	EXPRESSION_EXPECTED Expression expected.
static int	INVALID_OPERAND Invalid operand.
static int	INVALID_OPERATOR Invalid operator.
static int	NO_ERROR No error.
static int	NO_FUNC_DEFINITION No function definition to parse.
static int	OPERATOR_EXPECTED Operator expected.
static int	PAREN_EXPECTED Parentheses expected.
static int	PAREN_NOT_MATCH Parenthesis mismatch.
static int	REF_NAME_EXPECTED Referenced name could not be found.
static int	STACK_OVERFLOW Stack overflow.
static int	SYNTAX_ERROR Syntax error.
static int	TOO_MANY_CONSTS Too many constants.
static int	UNCOMPILED_FUNCTION Attempt to evaluate an uncompiled function.
static int	UNKNOWN_IDENTIFIER Unknown identifier.

Constructor Summary

ParserSuryono(int variablecount)
The constructor of Parser.

Method Summary

void	define(java.lang.String definition) Defines a function.
void	defineVariable(int index, java.lang.String name) Sets the variable names.
double	evaluate() Evaluates compiled function.
int	getErrorCode() Gets error code of last operation.
int	getErrorPosition() Gets error position.
java.lang.String	getErrorString() Gets error string/message of last operation.
static java.lang.String[]	getVariableList(java.lang.String _expression) Gets an expression and returns a String[] of the variables the expression will need.
static java.util.Vector<java.lang.String>	getVariableList(java.lang.String _expression, java.util.Vector<java.lang.String> varlist) Gets an expression and a Vector of declared variables and updates the Vector with extra variables the expression will need.
static boolean	isKeyword(java.lang.String token) Wether a given token is a reserved word
void	parse() Parses defined function.
void	setVariable(int index, double value) Sets the variable value.
static java.lang.String	toErrorString(int errorcode) Converts error code to error string.

Methods inherited from class java.lang.Object

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

Field Detail

NO_ERROR

public static final int NO_ERROR

No error.

See Also:

Constant Field Values

SYNTAX_ERROR

public static final int SYNTAX_ERROR

Syntax error.

See Also:

Constant Field Values

PAREN_EXPECTED

public static final int PAREN_EXPECTED

Parentheses expected.

See Also:

Constant Field Values

UNCOMPILED_FUNCTION

public static final int UNCOMPILED_FUNCTION

Attempt to evaluate an uncompiled function.

See Also:

Constant Field Values

EXPRESSION_EXPECTED

public static final int EXPRESSION_EXPECTED

Expression expected.

See Also:

Constant Field Values

UNKNOWN_IDENTIFIER

public static final int UNKNOWN_IDENTIFIER

Unknown identifier.

See Also:

Constant Field Values

OPERATOR_EXPECTED

public static final int OPERATOR_EXPECTED

Operator expected.

See Also:

Constant Field Values

PAREN_NOT_MATCH

public static final int PAREN_NOT_MATCH

Parenthesis mismatch.

See Also:

Constant Field Values

CODE_DAMAGED

public static final int CODE_DAMAGED

Code damaged.

See Also:

Constant Field Values

STACK_OVERFLOW

public static final int STACK_OVERFLOW

Stack overflow.

See Also:

Constant Field Values

TOO_MANY_CONSTS

public static final int TOO_MANY_CONSTS

Too many constants.

See Also:

Constant Field Values

COMMA_EXPECTED

public static final int COMMA_EXPECTED

Comma expected.

See Also:

Constant Field Values

INVALID_OPERAND

public static final int INVALID_OPERAND

Invalid operand.

See Also:

Constant Field Values

INVALID_OPERATOR

public static final int INVALID_OPERATOR

Invalid operator.

See Also:

Constant Field Values

NO_FUNC_DEFINITION

public static final int NO_FUNC_DEFINITION

No function definition to parse.

See Also:

Constant Field Values

REF_NAME_EXPECTED

public static final int REF_NAME_EXPECTED

Referenced name could not be found.

See Also:

Constant Field Values

Constructor Detail

ParserSuryono

public ParserSuryono(int variablecount)

The constructor of Parser.

Parameters:

variablecount - the number of variables

Method Detail

isKeyword

public static boolean isKeyword(java.lang.String token)

Wether a given token is a reserved word

Parameters:

token -

Returns:

getVariableList

public static java.lang.String[] getVariableList(java.lang.String _expression)

Gets an expression and returns a String[] of the variables the expression will need. This can be used to decide beforehand how many variables a new parser should have.

getVariableList

public static java.util.Vector<java.lang.String> getVariableList(java.lang.String _expression,
                                                                 java.util.Vector<java.lang.String> varlist)

Gets an expression and a Vector of declared variables and updates the Vector with extra variables the expression will need. This can be used to decide beforehand how many variables a new parser should have.

Returns:

the same Vector updated

defineVariable

public void defineVariable(int index,
                           java.lang.String name)

Sets the variable names.

Parameters:

index - the variable index (one based)

name - the variable name

setVariable

public void setVariable(int index,
                        double value)

Sets the variable value. The variable is accessed by index.

Parameters:

index - the variable index (one based)

value - the variable value

define

public void define(java.lang.String definition)

Defines a function. Current postfix code becomes invalid.

Parameters:

definition - the function definition

parse

public void parse()

Parses defined function.

evaluate

public double evaluate()

Evaluates compiled function.

Returns:

the result of the function

getErrorCode

public int getErrorCode()

Gets error code of last operation.

Returns:

the error code

getErrorString

public java.lang.String getErrorString()

Gets error string/message of last operation.

Returns:

the error string

getErrorPosition

public int getErrorPosition()

Gets error position. Valid only if error code != NO_ERROR

Returns:

error position (one based)

toErrorString

public static java.lang.String toErrorString(int errorcode)

Converts error code to error string.

Returns:

the error string