org.nfunk.jep
Class JEP

java.lang.Object
  org.nfunk.jep.JEP

Direct Known Subclasses:

GroupJep, VectorJep, XJep

public class JEP
extends java.lang.Object

The JEP class is the main interface with which the user should interact. It contains all necessary methods to parse and evaluate expressions.

The most important methods are parseExpression(String), for parsing the mathematical expression, and getValue() for obtaining the value of the expression.

Visit http://www.singularsys.com/jep for the newest version of JEP, and complete documentation.

Since:

04/02/13 added Binom function

Author:

Nathan Funk

Field Summary

protected boolean	allowAssignment Allow undeclared variables option
protected boolean	allowUndeclared Allow undeclared variables option
protected java.util.Vector	errorList Error List
protected EvaluatorVisitor	ev Evaluator
protected FunctionTable	funTab Function Table
protected boolean	implicitMul Implicit multiplication option
protected NumberFactory	numberFactory Number factory
protected OperatorSet	opSet OperatorSet
protected Parser	parser The parser object
protected SymbolTable	symTab Symbol Table

Constructor Summary

	JEP() Creates a new JEP instance with the default settings.
	JEP(boolean traverse_in, boolean allowUndeclared_in, boolean implicitMul_in, NumberFactory numberFactory_in) Creates a new JEP instance with custom settings.
protected	JEP(JEP j) This constructor copies the SymbolTable and other components of the arguments to the new instance.

Method Summary

void	addComplex() Call this function if you want to parse expressions which involve complex numbers.
void	addConstant(java.lang.String name, java.lang.Object value) Adds a constant.
void	addFunction(java.lang.String functionName, PostfixMathCommandI function) Adds a new function to the parser.
void	addStandardConstants() Adds the constants pi and e to the parser.
void	addStandardFunctions() Adds the standard functions to the parser.
java.lang.Double	addVariable(java.lang.String name, double value) Adds a new variable to the parser, or updates the value of an existing variable.
Complex	addVariable(java.lang.String name, double re, double im) Adds a new complex variable to the parser, or updates the value of an existing variable.
void	addVariable(java.lang.String name, java.lang.Object object) Adds a new variable to the parser as an object, or updates the value of an existing variable.
java.lang.Object	evaluate(Node node) Evaluate an expression.
boolean	getAllowAssignment() Whether assignment equation y=x+1 equations are allowed.
boolean	getAllowUndeclared() Returns the value of the allowUndeclared option.
Complex	getComplexValue() Evaluates and returns the value of the expression as a complex number.
java.lang.String	getErrorInfo() Reports information on the errors that occurred during the most recent action.
EvaluatorVisitor	getEvaluatorVisitor() Returns the EvaluatorVisitor
FunctionTable	getFunctionTable() Returns the function table (the list of all functions that the parser recognizes).
boolean	getImplicitMul() Returns the value of the implicit multiplication option.
NumberFactory	getNumberFactory() Returns the number factory.
OperatorSet	getOperatorSet() Returns the operator set.
Parser	getParser() Returns the parse object.
SymbolTable	getSymbolTable() Returns the symbol table (the list of all variables that the parser recognizes).
Node	getTopNode() Returns the top node of the expression tree.
boolean	getTraverse() Returns the value of the traverse option.
double	getValue() Evaluates and returns the value of the expression as a double number.
java.lang.Object	getValueAsObject() Evaluates and returns the value of the expression as an object.
Variable	getVar(java.lang.String name) Gets the object representing the variable with a given name.
java.lang.Object	getVarValue(java.lang.String name) Returns the value of the variable with given name.
boolean	hasError() Returns true if an error occurred during the most recent action (parsing or evaluation).
void	initFunTab() Creates a new FunctionTable object as funTab.
void	initSymTab() Creates a new SymbolTable object as symTab.
Node	parse(java.lang.String expression) Parses an expression.
Node	parseExpression(java.lang.String expression_in) Parses the expression.
java.lang.Object	removeFunction(java.lang.String name) Removes a function from the parser.
java.lang.Object	removeVariable(java.lang.String name) Removes a variable from the parser.
void	setAllowAssignment(boolean value) Sets whether assignment equations like y=x+1 are allowed.
void	setAllowUndeclared(boolean value) Sets the value for the undeclared variables option.
void	setImplicitMul(boolean value) Sets the value of the implicit multiplication option.
void	setTraverse(boolean value) Sets the value of the traverse option. setTraverse is useful for debugging purposes.
void	setVarValue(java.lang.String name, java.lang.Object val) Sets the value of a variable.

Methods inherited from class java.lang.Object

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

Field Detail

allowUndeclared

protected boolean allowUndeclared

Allow undeclared variables option

allowAssignment

protected boolean allowAssignment

Allow undeclared variables option

implicitMul

protected boolean implicitMul

Implicit multiplication option

symTab

protected SymbolTable symTab

Symbol Table

funTab

protected FunctionTable funTab

Function Table

errorList

protected java.util.Vector errorList

Error List

parser

protected Parser parser

The parser object

ev

protected EvaluatorVisitor ev

Evaluator

numberFactory

protected NumberFactory numberFactory

Number factory

opSet

protected OperatorSet opSet

OperatorSet

Constructor Detail

JEP

public JEP()

Creates a new JEP instance with the default settings.

Traverse = false
Allow undeclared variables = false
Implicit multiplication = false
Number Factory = DoubleNumberFactory

JEP

public JEP(boolean traverse_in,
           boolean allowUndeclared_in,
           boolean implicitMul_in,
           NumberFactory numberFactory_in)

Creates a new JEP instance with custom settings. If the numberFactory_in is null, the default number factory is used.

Parameters:

traverse_in - The traverse option.

allowUndeclared_in - The "allow undeclared variables" option.

implicitMul_in - The implicit multiplication option.

numberFactory_in - The number factory to be used.

JEP

protected JEP(JEP j)

This constructor copies the SymbolTable and other components of the arguments to the new instance. Subclasses can call this protected constructor and set the individual components themselves.

Since:

2.3.0 alpha

Method Detail

initSymTab

public void initSymTab()

Creates a new SymbolTable object as symTab.

initFunTab

public void initFunTab()

Creates a new FunctionTable object as funTab.

addStandardFunctions

public void addStandardFunctions()

Adds the standard functions to the parser. If this function is not called before parsing an expression, functions such as sin() or cos() would produce an "Unrecognized function..." error. In most cases, this method should be called immediately after the JEP object is created.

Since:

2.3.0 alpha added if and exp functions, 2.3.0 beta 1 added str function

addStandardConstants

public void addStandardConstants()

Adds the constants pi and e to the parser. As addStandardFunctions(), this method should be called immediately after the JEP object is created.

addComplex

public void addComplex()

Call this function if you want to parse expressions which involve complex numbers. This method specifies "i" as the imaginary unit (0,1). Two functions re() and im() are also added for extracting the real or imaginary components of a complex number respectively.

Since:

2.3.0 alpha The functions cmod and arg are added to get the modulus and argument., 2.3.0 beta 1 The functions complex and polar to convert x,y and r,theta to Complex., Feb 05 added complex conjugate conj.

addFunction

public void addFunction(java.lang.String functionName,
                        PostfixMathCommandI function)

Adds a new function to the parser. This must be done before parsing an expression so the parser is aware that the new function may be contained in the expression.

Parameters:

functionName - The name of the function

function - The function object that is used for evaluating the function

addConstant

public void addConstant(java.lang.String name,
                        java.lang.Object value)

Adds a constant. This is a variable whose value cannot be changed.

Since:

2.3.0 beta 1

addVariable

public java.lang.Double addVariable(java.lang.String name,
                                    double value)

Adds a new variable to the parser, or updates the value of an existing variable. This must be done before parsing an expression so the parser is aware that the new variable may be contained in the expression.

Parameters:

name - Name of the variable to be added

value - Initial value or new value for the variable

Returns:

Double object of the variable

addVariable

public Complex addVariable(java.lang.String name,
                           double re,
                           double im)

Adds a new complex variable to the parser, or updates the value of an existing variable. This must be done before parsing an expression so the parser is aware that the new variable may be contained in the expression.

Parameters:

name - Name of the variable to be added

re - Initial real value or new real value for the variable

im - Initial imaginary value or new imaginary value for the variable

Returns:

Complex object of the variable

addVariable

public void addVariable(java.lang.String name,
                        java.lang.Object object)

Adds a new variable to the parser as an object, or updates the value of an existing variable. This must be done before parsing an expression so the parser is aware that the new variable may be contained in the expression.

Parameters:

name - Name of the variable to be added

object - Initial value or new value for the variable

removeVariable

public java.lang.Object removeVariable(java.lang.String name)

Removes a variable from the parser. For example after calling addStandardConstants(), removeVariable("e") might be called to remove the euler constant from the set of variables.

Returns:

The value of the variable if it was added earlier. If the variable is not in the table of variables, null is returned.

getVarValue

public java.lang.Object getVarValue(java.lang.String name)

Returns the value of the variable with given name.

Parameters:

name - name of the variable.

Returns:

the current value of the variable.

Since:

2.3.0 alpha

setVarValue

public void setVarValue(java.lang.String name,
                        java.lang.Object val)

Sets the value of a variable. The variable must exist before hand.

Parameters:

name - name of the variable.

val - the initial value of the variable.

Throws:

java.lang.NullPointerException - if the variable has not been previously created with addVariable(String,Object) first.

Since:

2.3.0 alpha, April 05 - throws an exception if variable unset.

getVar

public Variable getVar(java.lang.String name)

Gets the object representing the variable with a given name.

Parameters:

name - the name of the variable to find.

Returns:

the Variable object or null if name not found.

Since:

2.3.0 alpha

removeFunction

public java.lang.Object removeFunction(java.lang.String name)

Removes a function from the parser.

Returns:

If the function was added earlier, the function class instance is returned. If the function was not present, null is returned.

setTraverse

public void setTraverse(boolean value)

Sets the value of the traverse option. setTraverse is useful for debugging purposes. When traverse is set to true, the parse-tree will be dumped to the standard output device.

The default value is false.

Parameters:

value - The boolean traversal option.

getTraverse

public boolean getTraverse()

Returns the value of the traverse option.

Returns:

True if the traverse option is enabled. False otherwise.

setImplicitMul

public void setImplicitMul(boolean value)

Sets the value of the implicit multiplication option. If this option is set to true before parsing, implicit multiplication will be allowed. That means that an expression such as

"1 2"

is valid and is interpreted as

"1*2"

.

The default value is false.

Parameters:

value - The boolean implicit multiplication option.

getImplicitMul

public boolean getImplicitMul()

Returns the value of the implicit multiplication option.

Returns:

True if the implicit multiplication option is enabled. False otherwise.

setAllowUndeclared

public void setAllowUndeclared(boolean value)

Sets the value for the undeclared variables option. If this option is set to true, expressions containing variables that were not previously added to JEP will not produce an "Unrecognized Symbol" error. The new variables will automatically be added while parsing, and initialized to 0.

If this option is set to false, variables that were not previously added to JEP will produce an error while parsing.

The default value is false.

Parameters:

value - The boolean option for allowing undeclared variables.

getAllowUndeclared

public boolean getAllowUndeclared()

Returns the value of the allowUndeclared option.

Returns:

True if the allowUndeclared option is enabled. False otherwise.

setAllowAssignment

public void setAllowAssignment(boolean value)

Sets whether assignment equations like y=x+1 are allowed.

Since:

2.3.0 alpha

getAllowAssignment

public boolean getAllowAssignment()

Whether assignment equation y=x+1 equations are allowed.

Since:

2.3.0 alpha

parseExpression

public Node parseExpression(java.lang.String expression_in)

Parses the expression. If there are errors in the expression, they are added to the errorList member. Errors can be obtained through getErrorInfo().

Parameters:

expression_in - The input expression string

Returns:

the top node of the expression tree if the parse was successful, null otherwise

parse

public Node parse(java.lang.String expression)
           throws ParseException

Parses an expression. Returns a object of type Node, does not catch errors. Does not set the topNode variable of the JEP instance. This method should generally be used with the evaluate method rather than getValueAsObject.

Parameters:

expression - represented as a string.

Returns:

The top node of a tree representing the parsed expression.

Throws:

ParseException

Since:

2.3.0 alpha, 2.3.0 beta - will raise exception if errorList non empty

evaluate

public java.lang.Object evaluate(Node node)
                          throws ParseException

Evaluate an expression. This method evaluates the argument rather than the topNode of the JEP instance. It should be used in conjunction with parse rather than parseExpression.

Parameters:

node - the top node of the tree representing the expression.

Returns:

The value of the expression

Throws:

ParseException - if for some reason the expression could not be evaluated

java.lang.RuntimeException - could potentially be thrown.

Since:

2.3.0 alpha

getValue

public double getValue()

Evaluates and returns the value of the expression as a double number.

Returns:

The calculated value of the expression as a double number. If the type of the value does not implement the Number interface (e.g. Complex), NaN is returned. If an error occurs during evaluation, NaN is returned and hasError() will return true.

See Also:

getComplexValue()

getComplexValue

public Complex getComplexValue()

Evaluates and returns the value of the expression as a complex number.

Returns:

The calculated value of the expression as a complex number if no errors occur. Returns null otherwise.

getValueAsObject

public java.lang.Object getValueAsObject()

Evaluates and returns the value of the expression as an object. The EvaluatorVisitor member ev is used to do the evaluation procedure. This method is useful when the type of the value is unknown, or not important.

Returns:

The calculated value of the expression if no errors occur. Returns null otherwise.

hasError

public boolean hasError()

Returns true if an error occurred during the most recent action (parsing or evaluation).

Returns:

Returns true if an error occurred during the most recent action (parsing or evaluation).

getErrorInfo

public java.lang.String getErrorInfo()

Reports information on the errors that occurred during the most recent action.

Returns:

A string containing information on the errors, each separated by a newline character; null if no error has occurred

getTopNode

public Node getTopNode()

Returns the top node of the expression tree. Because all nodes are pointed to either directly or indirectly, the entire expression tree can be accessed through this node. It may be used to manipulate the expression, and subsequently evaluate it manually.

Returns:

The top node of the expression tree

getSymbolTable

public SymbolTable getSymbolTable()

Returns the symbol table (the list of all variables that the parser recognizes).

Returns:

The symbol table

getFunctionTable

public FunctionTable getFunctionTable()

Returns the function table (the list of all functions that the parser recognizes).

Returns:

The function table

getEvaluatorVisitor

public EvaluatorVisitor getEvaluatorVisitor()

Returns the EvaluatorVisitor

Returns:

the EvaluatorVisitor.

getNumberFactory

public NumberFactory getNumberFactory()

Returns the number factory.

Returns:

the NumberFactory used by this JEP instance.

getOperatorSet

public OperatorSet getOperatorSet()

Returns the operator set.

Returns:

the OperatorSet used by this JEP instance.

Since:

2.3.0 alpha

getParser

public Parser getParser()

Returns the parse object.

Returns:

the Parse used by this JEP.

Since:

2.3.0 beta 1