tk.pratanumandal.expr4j

Class OperatorRepository

java.lang.Object

tk.pratanumandal.expr4j.OperatorRepository

public class OperatorRepository
extends Object

The OperatorRepository class is the repository of all operators, functions, variables, and constants in the environment.

This class can be used to create user defined functions. For example, we can create a function si(principal, rate, time) to calculate simple interest in the following manner:

        // using lambda expression
        OperatorRepository.addFunction("si", 3, (ops) -> {
                return new Operand((ops[0].toDouble() * ops[1].toDouble() * ops[2].toDouble()) / 100.0);
        });
        
        // using anonymous class
        OperatorRepository.addFunction("si", 3,
                new Function() {
                        @Override
                        public Operand evaluate(Operand ... ops) {
                                return new Operand((ops[0].toDouble() * ops[1].toDouble() * ops[2].toDouble()) / 100.0);
                        }
                }
        );
 

Since:

0.0.2

Author:

Pratanu Mandal

Field Summary

Fields

Modifier and Type	Field and Description
protected static Map<String,Operator.Properties>	OPERATORS A map of all operators, functions, variables, and constants supported.
protected static List<String>	PREDEFINED_OPERATORS A list of all predefined operators, functions, variables, and constants.

Method Summary

Modifier and Type	Method and Description
static void	addFunction(String fName, Function function) Utility method to add user defined function with variable number of parameters to the environment. Method names can consist of lowercase letters, uppercase letters, and digits.
static void	addFunction(String fName, int params, Function function) Utility method to add user defined function to the environment. Method names can consist of lowercase letters, uppercase letters, and digits.
static List<String>	getOperatorList() Utility method to get list of all operator names currently supported by the environment. The returned list is sorted lexicographically by operator names.
static Operator.Properties	getOperatorProperties(String value) Utility method to get the properties of an operator.
static boolean	isFunction(String op) Utility method to determine if a string is a supported function.
static boolean	isOperator(String op) Utility method to determine if a string is a supported operator.
static boolean	isVariableOrConstant(String op) Utility method to determine if a string is a supported variable or constant.
static void	removeFunction(String fName) Utility method to remove user defined function from the environment. Method names can consist of lowercase letters, uppercase letters, and digits.

Methods inherited from class java.lang.Object

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

Field Detail

OPERATORS

protected static final Map<String,Operator.Properties> OPERATORS

A map of all operators, functions, variables, and constants supported.

PREDEFINED_OPERATORS

protected static final List<String> PREDEFINED_OPERATORS

A list of all predefined operators, functions, variables, and constants.

Method Detail

getOperatorProperties

public static Operator.Properties getOperatorProperties(String value)

Utility method to get the properties of an operator.

Parameters:

value - The operator value as a string

Returns:

The properties of the operator

isOperator

public static boolean isOperator(String op)

Utility method to determine if a string is a supported operator.

Parameters:

op - The string to check

Returns:

true if the string is a supported operator, otherwise false

isFunction

public static boolean isFunction(String op)

Utility method to determine if a string is a supported function.

Parameters:

op - The string to check

Returns:

true if the string is a supported function, otherwise false

isVariableOrConstant

public static boolean isVariableOrConstant(String op)

Utility method to determine if a string is a supported variable or constant.

Parameters:

op - The string to check

Returns:

true if the string is a supported variable or constant, otherwise false

addFunction

public static void addFunction(String fName,
                               int params,
                               Function function)

Utility method to add user defined function to the environment.
Method names can consist of lowercase letters, uppercase letters, and digits. However, first character must not be a digit.

Parameters:

fName - Function name - e.g. for function name 'myFunc', it will be called as myFunc(...)

params - Number of parameters

function - Function definition

addFunction

public static void addFunction(String fName,
                               Function function)

Utility method to add user defined function with variable number of parameters to the environment.
Method names can consist of lowercase letters, uppercase letters, and digits. However, first character must not be a digit.

Parameters:

fName - Function name - e.g. for function name 'myFunc', it will be called as myFunc(...)

function - Function definition

removeFunction

public static void removeFunction(String fName)

Utility method to remove user defined function from the environment.
Method names can consist of lowercase letters, uppercase letters, and digits. However, first character must not be a digit.

Parameters:

fName - Function name - e.g. for function name 'myFunc', it will be called as myFunc(...)

getOperatorList

public static List<String> getOperatorList()

Utility method to get list of all operator names currently supported by the environment.
The returned list is sorted lexicographically by operator names.

Returns:

List of operator names currently supported by the environment