Package com.singularsys.jep

Class Jep

java.lang.Object
com.singularsys.jep.Jep
All Implemented Interfaces:
Serializable
public class Jep extends Object implements 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();
 try {
   jep.addVariable("x", 10);
         jep.parse("x+1");
         Object result = jep.evaluate();
         System.out.println("x + 1 = " + result);
 } catch (JepException e) {
         System.out.println("An error occurred: " + e.toString());
 }

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

See Also:

  • Field Details

    • 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 OperatorTableI 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

    • additionalComponents

      protected final List<JepComponent> additionalComponents
      Additional components outside the standard set

    • implicitMul

      protected boolean implicitMul
      Implicit Multiplication option

    • allowUndeclared

      protected boolean allowUndeclared
      Allow Undeclared Variables option

    • allowAssignment

      protected boolean allowAssignment
      Allow Assignment option

  • Constructor Details

    • 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. If the full set of components is not specified then default components will be used.
      Parameters:
      components - a set of components which are used to build this Jep instance
      Since:
      3.3 now varargs, default components used

  • Method Details

    • setComponent

      public void setComponent(JepComponent component)
      Sets a single component. The component passed in as a parameter overrides the active component and the active component is no longer used. reinitializeComponents() is called after the component is added.
      Parameters:
      component - The component to be set.

    • setComponents

      public void setComponents(JepComponent... components)
      Sets one or more components for this Jep instance. The current components are overridden by the components passed in. 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.

    • addDefaultComponents

      protected void addDefaultComponents()
      Set the default values for components if none are specified. Called after any components specified in the constructor has been set.

    • setComponentsInternal

      protected void setComponentsInternal(ComponentSet compSet)

    • setComponentInternal

      protected void setComponentInternal(JepComponent comp)
      Identifies the type of comp and set the associated member accordingly. This overrides the current component set.
      Parameters:
      comp - The component 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.

    • getNumberFactory

      public NumberFactory getNumberFactory()
      Returns the number factory
      Returns:
      number factor used

    • getNodeFactory

      public NodeFactory getNodeFactory()
      Returns the node factory
      Returns:
      node factory used

    • getVariableFactory

      public VariableFactory getVariableFactory()
      Returns the variable factory
      Returns:
      variable factory used

    • getFunctionTable

      public FunctionTable getFunctionTable()
      Returns the function table
      Returns:
      Function table used

    • getOperatorTable

      public OperatorTableI getOperatorTable()
      Returns the operator table
      Returns:
      Operator table used

    • getVariableTable

      public VariableTable getVariableTable()
      Returns the variable table
      Returns:
      variable table used

    • getParser

      public Parser getParser()
      Returns the parser
      Returns:
      parser used

    • getEvaluator

      public Evaluator getEvaluator()
      Returns the evaluator
      Returns:
      evaluator used

    • getPrintVisitor

      public PrintVisitor getPrintVisitor()
      Returns the print visitor
      Returns:
      print visitor used

    • getAdditionalComponents

      public List<JepComponent> getAdditionalComponents()
      Returns the additional components. Any modification to the list should be followed by a call to reinitializeComponents(). New components should be added by calling setComponent(JepComponent).
      Returns:
      the list

    • addVariable

      public Variable addVariable(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(String name, Object value) throws JepException
      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
      Throws:
      JepException - if an attempt is made to set the value of a constant variable

    • setVariable

      public Variable setVariable(String name, 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, return null if error setting variable
      Since:
      Jep 3.5

    • addVariable

      public Variable addVariable(String name, double value) throws JepException
      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
      Throws:
      JepException - if an attempt is made to set the value of a constant variable

    • addVariable

      public Variable addVariable(String name, double re, double im) throws JepException
      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
      Throws:
      JepException - if an attempt is made to set the value of a constant variable

    • addConstant

      public Variable addConstant(String name, Object value) throws JepException
      Add a constant: a variable whose value cannot be changed.
      Parameters:
      name - constants name
      value - its value
      Returns:
      the corresponding Variable
      Throws:
      JepException - if a constant variable already exists

    • tryAddConstant

      public boolean tryAddConstant(String name, Object value)
      Tries to add a constant.
      Parameters:
      name - name of constant
      value - value of constant
      Returns:
      true if successfully added or a constant with same name and value already exists. false if the constant has a different value

    • 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(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 Object getVariableValue(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).
      Parameters:
      value - true is assignment equations are allowed, false otherwise

    • getAllowAssignment

      public boolean getAllowAssignment()
      Whether assignment equation y=x+1 equations are allowed.
      Returns:
      true is assignment equations are allowed, 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 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 Object getDefaultValue()
      Returns the default value used for new variables.
      Returns:
      the value

    • setDefaultValue

      public void setDefaultValue(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 - value new variables have if not explicitly given
      See Also:

    • 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(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:
      null unless there was a previous function with the same name in which case return the previous pfmc

    • 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(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 - if there is a syntax error in expression

    • parse

      public Node parse(String str) throws ParseException
      Parses a string.
      Parameters:
      str - the input string
      Returns:
      the root node of the parse tree
      Throws:
      ParseException - if there is a syntax error in expression

    • initMultiParse

      public void initMultiParse(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 semicolons.
      See Also:

    • initMultiParse

      public void initMultiParse(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 semicolons will be read.
      See Also:

    • 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 
       Jep j = new Jep();
 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 - if there is a syntax error in expression
      See Also:

    • 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 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 Object evaluate(Node node) throws EvaluationException
      Evaluates the expression tree pointed to by the node parameter.
      Parameters:
      node - root of expression tree to be evaluated
      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, 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, 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 String toString(Node node)
      Returns a string representation of an expression.
      Parameters:
      node - root node of the expression.
      Returns:
      string representation

    • rootNodeToString

      public String rootNodeToString()
      Returns a string representation of the last expression parsed.
      Returns:
      string representation