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## com.singularsys.jep
Class Jep

    java.lang.Object
      com.singularsys.jep.Jep

All Implemented Interfaces:
  java.io.Serializable

    public class Jep

extends java.lang.Object
implements java.io.Serializable

The Jep class is the main interface with which the user should interact. It contains all necessary methods to parse and evaluate expressions. To evaluate an expression, simply call the `parse(String)` and `evaluate` methods after each other. The following code snippet shows a parsing and evaluating a simple expression with a single variable:

    Jep jep = new Jep();
    jep.addVariable("x", 10);
    try {
            jep.parse("x+1");
            Object result = jep.evaluate();
            System.out.println("x + 1 = " + result);
    } catch (Exception e) {
            System.out.println("An error occured: " + e.getMessage());
    }

The class is serializable. Please see the documentation section "Serialization" for more information on the various options for serializing.

See Also:
  Serialized Form

Field Summary
`protected boolean` | `allowAssignment` Allow Assignment option
`protected boolean` | `allowUndeclared` Allow Undeclared Variables option
`protected Evaluator` | `evaluator` Evaluator instance used for evaluating parse trees
`protected FunctionTable` | `funTab` Function Table
`protected boolean` | `implicitMul` Implicit Multiplication option
`protected Node` | `lastRootNode` Root node of the last parsed expression
`protected NodeFactory` | `nodeFac` Node Factory
`protected NumberFactory` | `numFac` Number Factory
`protected OperatorTable` | `opTab` Operator Table
`protected Parser` | `parser` Parser instance used for parsing expressions
`protected PrintVisitor` | `pv` PrintVisitor
`protected VariableFactory` | `varFac` Variable Factory
`protected VariableTable` | `varTab` Variable Table

Constructor Summary
`Jep()` Creates a new Jep instance using the standard components with default settings.
`Jep(ComponentSet compSet)` Creates a new Jep instance with a specific component set.
`Jep(JepComponent[] components)` Creates a new Jep instance with a set of components specified by an array of components.

Method Summary
`Variable` | `addConstant(java.lang.String name, java.lang.Object value)` Add a constant: a variable who's value cannot be changed.
`PostfixMathCommandI` | `addFunction(java.lang.String name, PostfixMathCommandI pfmc)` Adds a function to the parser.
`boolean` | `addStandardConstants()` Adds the constants pi and e to the parser.
`Variable` | `addVariable(java.lang.String name)` Adds a variable with a given name.
`Variable` | `addVariable(java.lang.String name, double value)` Adds or sets a double variable with a given name and value.
`Variable` | `addVariable(java.lang.String name, double re, double im)` Adds or sets a complex variable with a given name and value.
`Variable` | `addVariable(java.lang.String name, java.lang.Object value)` Adds or sets a variable with a given name and value.
`Node` | `continueParsing()` Continue parsing without re-initialising the stream.
`java.lang.Object` | `evaluate()` Evaluates the most recently parsed expression.
`java.lang.Object` | `evaluate(Node node)` Evaluates the expression tree pointed to by the node parameter.
`double` | `evaluateD()` Evaluates the most recently parsed expression and returns the result as a double.
`boolean` | `getAllowAssignment()` Whether assignment equation `y=x+1` equations are allowed.
`boolean` | `getAllowUndeclared()` Returns the value of the allowUndeclared option.
`java.lang.Object` | `getDefaultValue()` Returns the default value used for new variables.
`Evaluator` | `getEvaluator()` Returns the evaluator
`FunctionTable` | `getFunctionTable()` Returns the function table
`boolean` | `getImplicitMul()` Returns the value of the implicit multiplication option.
`Node` | `getLastRootNode()` Returns the root node of the last successfully parsed expression
`NodeFactory` | `getNodeFactory()` Returns the node factory
`NumberFactory` | `getNumberFactory()` Returns the number factory
`OperatorTable` | `getOperatorTable()` Returns the operator table
`Parser` | `getParser()` Returns the parser
`PrintVisitor` | `getPrintVisitor()` Returns the print visitor
`Variable` | `getVariable(java.lang.String name)` Returns the `Variable` instance of the variable `name`.
`VariableFactory` | `getVariableFactory()` Returns the variable factory
`VariableTable` | `getVariableTable()` Returns the variable table
`java.lang.Object` | `getVariableValue(java.lang.String name)` Returns the value of the variable `name`.
`void` | `initMultiParse(java.io.Reader reader)` Initialises the parser with a Reader for parsing with multiple expressions.
`void` | `initMultiParse(java.lang.String str)` Initialises the parser for parsing a string with multiple expressions.
`Node` | `parse(java.io.Reader reader)` Parses the input from a Reader.
`Node` | `parse(java.lang.String str)` Parses a string.
`void` | `print()` Print the last parsed expression to System.out.
`void` | `print(Node node)` Print an expression to System.out.
`void` | `print(Node node, java.io.PrintStream out)` Print an expression to a given stream.
`void` | `println()` Print the last parsed expression to System.out with a new line.
`void` | `println(Node node)` Print an expression to System.out with a new line.
`void` | `println(Node node, java.io.PrintStream out)` Print an expression to a given stream with a newline.
`void` | `reinitializeComponents()` Calls the `init` method of all components.
`java.lang.String` | `rootNodeToString()` Returns a string representation of the last expression parsed.
`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` | `setComponent(JepComponent component)` Sets a single component.
`void` | `setComponents(JepComponent[] components)` Sets one or more components for this Jep instance.
`void` | `setDefaultValue(java.lang.Object defaultValue)` Sets the default value used for new variables.
`void` | `setImplicitMul(boolean value)` Sets the value of the implicit multiplication option.
`java.lang.String` | `toString(Node node)` Returns a string representation of an expression.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### numFac

    protected NumberFactory numFac

  Number Factory

### varFac

    protected VariableFactory varFac

  Variable Factory

### nodeFac

    protected NodeFactory nodeFac

  Node Factory

### varTab

    protected VariableTable varTab

  Variable Table

### funTab

    protected FunctionTable funTab

  Function Table

### opTab

    protected OperatorTable opTab

  Operator Table

### pv

    protected PrintVisitor pv

  PrintVisitor

### lastRootNode

    protected transient Node lastRootNode

  Root node of the last parsed expression

### parser

    protected Parser parser

  Parser instance used for parsing expressions

### evaluator

    protected Evaluator evaluator

  Evaluator instance used for evaluating parse trees

### implicitMul

    protected boolean implicitMul

  Implicit Multiplication option

### allowUndeclared

    protected boolean allowUndeclared

  Allow Undeclared Variables option

### allowAssignment

    protected boolean allowAssignment

  Allow Assignment option

Constructor Detail

### Jep

    public Jep()

  Creates a new Jep instance using the standard components with default settings. The StandardComponents component set is used.

### Jep

    public Jep(ComponentSet compSet)

  Creates a new Jep instance with a specific component set.

  Parameters:
    `compSet` - The component set to be used.

### Jep

    public Jep(JepComponent[] components)

  Creates a new Jep instance with a set of components specified by an array of components.

  Parameters:
    `components` - An array of components to initialize Jep with.

Method Detail

### setComponents

    public void setComponents(JepComponent[] components)

  Sets one or more components for this Jep instance. Each component can be one of the following:
  - NumberFactory
  - VariableFactory
  - NodeFactory
  - VariableTable
  - FunctionTable
  - OperatorTable
  - Parser
  - Evaluator

  Parameters:
    `components` - An array of components to be set.

### reinitializeComponents

    public void reinitializeComponents()

  Calls the `init` method of all components. This is necessary in a few cases such as after adding new operators to the configurable parser.

### setComponent

    public void setComponent(JepComponent component)

  Sets a single component. This is done by calling setComponents with a single element array parameter.

  Parameters:
    `component` - The component to be set.

### getNumberFactory

    public NumberFactory getNumberFactory()

  Returns the number factory

### getNodeFactory

    public NodeFactory getNodeFactory()

  Returns the node factory

### getVariableFactory

    public VariableFactory getVariableFactory()

  Returns the variable factory

### getFunctionTable

    public FunctionTable getFunctionTable()

  Returns the function table

### getOperatorTable

    public OperatorTable getOperatorTable()

  Returns the operator table

### getVariableTable

    public VariableTable getVariableTable()

  Returns the variable table

### getParser

    public Parser getParser()

  Returns the parser

### getEvaluator

    public Evaluator getEvaluator()

  Returns the evaluator

### getPrintVisitor

    public PrintVisitor getPrintVisitor()

  Returns the print visitor

### addVariable

    public Variable addVariable(java.lang.String name)

  Adds a variable with a given name. The value is undefined. If the variable already exists, no changes are made.

  Parameters:
    `name` - the name of the variable to be added
  Returns:
    the `Variable` instance

### addVariable

    public Variable addVariable(java.lang.String name,
                                java.lang.Object value)

  Adds or sets a variable with a given name and value. If a variable with the same name already exists, the value of that variable is updated.

  Parameters:
    `name` - the name of the variable to be added
    `value` - the value of the variable to be added
  Returns:
    the `Variable` instance

### addVariable

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

  Adds or sets a double variable with a given name and value. If a variable with the same name already exists, the value of that variable is updated.

  Parameters:
    `name` - the name of the variable to be added
    `value` - the value of the variable to be added
  Returns:
    the `Variable` instance

### addVariable

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

  Adds or sets a complex variable with a given name and value. If a variable with the same name already exists, the value of that variable is updated.

  Parameters:
    `name` - the name of the variable to be added
    `re` - the real component of the variable to be added
    `im` - the imaginary component of the variable to be added
  Returns:
    the `Variable` instance

### addConstant

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

  Add a constant: a variable who's value cannot be changed.

  Parameters:
    `name` -
    `value` -
  Returns:
    the corresponding Variable

### addStandardConstants

    public boolean addStandardConstants()

  Adds the constants pi and e to the parser. The values are added as the Math.PI and Math.E values.

  Returns:
    true if successful, false otherwise

### getVariable

    public Variable getVariable(java.lang.String name)

  Returns the `Variable` instance of the variable `name`. If the variable has not been added, null is returned.

  Parameters:
    `name` - the name of the variable
  Returns:
    the `Variable` instance, or null if the variable has not been added.

### getVariableValue

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

  Returns the value of the variable `name`. If the variable has not been added, or if it's value is `null`, `null` is returned.

  Parameters:
    `name` - the name of the variable
  Returns:
    the value of the variable, or null if the variable has not been added or has the value null.

### setAllowAssignment

    public void setAllowAssignment(boolean value)

  Sets whether assignment equations like `y=x+1` are allowed. The default is true (assignment allowed).

### getAllowAssignment

    public boolean getAllowAssignment()

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

### 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 be automatically be added while parsing, and initialized to 0. Note this only affects the parsing stage, EvaluationException will still be thrown when trying to evaluate a variable with an undefined value.

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

  The default value is true.

  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.

### 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 true.

  Parameters:
    `value` - The boolean implicit multiplication option.

### getDefaultValue

    public java.lang.Object getDefaultValue()

  Returns the default value used for new variables.

  Returns:
    the value

### setDefaultValue

    public void setDefaultValue(java.lang.Object defaultValue)

  Sets the default value used for new variables. If the value is null (the default) then exceptions will be thrown when trying to evaluate the variables which do not have values set.

  Parameters:
    `defaultValue` -
  See Also:
    `StandardEvaluator.setTrapNullValues(boolean)`

### getImplicitMul

    public boolean getImplicitMul()

  Returns the value of the implicit multiplication option.

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

### addFunction

    public PostfixMathCommandI addFunction(java.lang.String name,
                                           PostfixMathCommandI pfmc)

  Adds a function to the parser.

  Parameters:
    `name` - the name of the function
    `pfmc` - the function class instance to be used to evaluate the function
  Returns:
    the function class added

### getLastRootNode

    public Node getLastRootNode()

  Returns the root node of the last successfully parsed expression

  Returns:
    the root node of the last successfully parsed expression

### parse

    public Node parse(java.io.Reader reader)
               throws ParseException

  Parses the input from a Reader.

  Parameters:
    `reader` - the input reader
  Returns:
    the root node of the parse tree
  Throws:
    `ParseException`

### parse

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

  Parses a string.

  Parameters:
    `str` - the input string
  Returns:
    the root node of the parse tree
  Throws:
    `ParseException`

### initMultiParse

    public void initMultiParse(java.lang.String str)

  Initialises the parser for parsing a string with multiple expressions. This method does not perform any parsing. Use continueParsing to parse the first expression and subsequent expressions from the input.

  Parameters:
    `str` - String containing a sequence of expressions separated by semi-colons.
  See Also:
    `continueParsing()`

### initMultiParse

    public void initMultiParse(java.io.Reader reader)

  Initialises the parser with a Reader for parsing with multiple expressions. This method does not perform any parsing. Use continueParsing to parse the first expression and subsequent expressions from the input.

  Parameters:
    `reader` - Reader from which equations separated by semi-colons will be read.
  See Also:
    `continueParsing()`

### continueParsing

    public Node continueParsing()
                         throws ParseException

  Continue parsing without re-initialising the stream. This requires initMultiParse to be called first. Allows re-entrance of parser so that strings like "x=1; y=2; z=3;" can be parsed. When a semicolon is encountered parsing finishes leaving the rest of the string unparsed. Parsing can be resumed from the current position by using this method. For example

       XJep j = new XJep();
       j.initMultiParse("x=1;y=2; z=3;");
       Node node;
       try {
       while((node = j.continueParsing())!=null) {
          j.println(node);
       } }catch(ParseException e) {}

  Empty equations such as "x=1;;y=2" are silently ignored, in this case the second call will return the node representing y=2.

  Returns:
    top node of equation parsed to date or null at EOF.
  Throws:
    `ParseException`
  See Also:
    `initMultiParse(String)`

### evaluateD

    public double evaluateD()
                     throws EvaluationException

  Evaluates the most recently parsed expression and returns the result as a double.

  Returns:
    Returns the value of the expression tree. If node is null, null is returned.
  Throws:
    `EvaluationException` - if an error occurs while evaluating or if the returned data type can not be converted to a `double` number.

### evaluate

    public java.lang.Object evaluate()
                              throws EvaluationException

  Evaluates the most recently parsed expression.

  Returns:
    Returns the value of the expression tree. If node is null, null is returned.
  Throws:
    `EvaluationException` - if an error occurs

### evaluate

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

  Evaluates the expression tree pointed to by the node parameter.

  Returns:
    Returns the value of the expression tree. If node is null, null is returned.
  Throws:
    `EvaluationException` - if an error occurs

### print

    public void print(Node node,
                      java.io.PrintStream out)

  Print an expression to a given stream.

  Parameters:
    `node` - root node of the expression to print
    `out` - stream to print to

### print

    public void print(Node node)

  Print an expression to System.out.

  Parameters:
    `node` - root node of the expression to print

### print

    public void print()

  Print the last parsed expression to System.out.

### println

    public void println(Node node,
                        java.io.PrintStream out)

  Print an expression to a given stream with a newline.

  Parameters:
    `node` - root node of the expression to print
    `out` - stream to print to

### println

    public void println(Node node)

  Print an expression to System.out with a new line.

  Parameters:
    `node` - root node of the expression to print

### println

    public void println()

  Print the last parsed expression to System.out with a new line.

### toString

    public java.lang.String toString(Node node)

  Returns a string representation of an expression.

  Parameters:
    `node` - root node of the expression.
  Returns:
    string representation

### rootNodeToString

    public java.lang.String rootNodeToString()

  Returns a string representation of the last expression parsed.

  Returns:
    string representation

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Copyright © 2008 Singular Systems http://www.singularsys.com/jep