edu.davidson.numerics
Class Parser

java.lang.Object
  |
  +--edu.davidson.numerics.Parser

public final class Parser

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(1,"x");     // lets the variable be 'x'
 parser.define("sin(x)/x");        // defines function: sin(x)/x
 parser.parse();                   // parses the function
 
 // calculates: sin(x)/x with x = -5.0 .. +5.0 in 20 steps
 // and prints the result to standard output.

 float result;
 for (i=-10; i <= 10; i++) {
   parser.setVariable(1,(float)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

Parser(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.
double	evaluate(double x)
double	evaluate(double[] v)
double	evaluate(double x, double y)
int	getErrorCode() Gets error code of last operation.
int	getErrorPosition() Gets error position.
java.lang.String	getErrorString() Gets error string/message of last operation.
java.lang.String	getFunctionString() Gets function string of last operation.
void	parse() Parses defined function.
void	setVariable(int index, double value) Sets the variable value.
void	setVariable(java.lang.String name, double value) Sets the variable value.
static java.lang.String	toErrorString(int errorcode) Converts error code to error string.
void	useDegree() Sets the angle unit to degree.
void	useRadian() Sets the angle unit to radian.

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.

SYNTAX_ERROR

public static final int SYNTAX_ERROR

Syntax error.

PAREN_EXPECTED

public static final int PAREN_EXPECTED

Parentheses expected.

UNCOMPILED_FUNCTION

public static final int UNCOMPILED_FUNCTION

Attempt to evaluate an uncompiled function.

EXPRESSION_EXPECTED

public static final int EXPRESSION_EXPECTED

Expression expected.

UNKNOWN_IDENTIFIER

public static final int UNKNOWN_IDENTIFIER

Unknown identifier.

OPERATOR_EXPECTED

public static final int OPERATOR_EXPECTED

Operator expected.

PAREN_NOT_MATCH

public static final int PAREN_NOT_MATCH

Parenthesis mismatch.

CODE_DAMAGED

public static final int CODE_DAMAGED

Code damaged.

STACK_OVERFLOW

public static final int STACK_OVERFLOW

Stack overflow.

TOO_MANY_CONSTS

public static final int TOO_MANY_CONSTS

Too many constants.

COMMA_EXPECTED

public static final int COMMA_EXPECTED

Comma expected.

INVALID_OPERAND

public static final int INVALID_OPERAND

Invalid operand.

INVALID_OPERATOR

public static final int INVALID_OPERATOR

Invalid operator.

NO_FUNC_DEFINITION

public static final int NO_FUNC_DEFINITION

No function definition to parse.

REF_NAME_EXPECTED

public static final int REF_NAME_EXPECTED

Referenced name could not be found.

Constructor Detail

Parser

public Parser(int variablecount)

The constructor of Parser.

Parameters:

variablecount - the number of variables

Method Detail

useRadian

public void useRadian()

Sets the angle unit to radian. Default upon construction.

useDegree

public void useDegree()

Sets the angle unit to degree.

defineVariable

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

Sets the variable names. Nothing happens if variable index > number of variables.

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. Nothing happens if variable index > number of variables.

Parameters:

index - the variable index (one based)

value - the variable value

setVariable

public void setVariable(java.lang.String name,
                        double value)

Sets the variable value. The variable is accessed by name. Nothing happens if variable could not be found.

Parameters:

name - the variable name

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(double x,
                       double y)

evaluate

public double evaluate(double x)

evaluate

public double evaluate(double[] v)

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

getFunctionString

public java.lang.String getFunctionString()

Gets function string of last operation.

Returns:

the function string