- JavaDoc

# JEP

- Introduction
- Basic Usage
- Variables
- Data types
- Operators
- Functions
- BigDecimal
- Manipulating Expressions
- Components
- Configurable Parser
- Grammar
- FAQ
- Migration
- Version History

# BigDecimal Mode

With JEP 3, it is now possible to evaluate expressions using decimal arithmetic. This allows calculations to be performed with specified accuracy or even unlimited accuracy. If you are running into precision problems or already know that you will require the highest possible precision in your calculations, we recommend using this operation mode.

Rather than using the `double` type to represent numbers, `BigDecimal` is used. The `BigDecimal` class is part of the Java API and is contained in the `java.math` package. For more information on this class, please read the Sun JavaDocs for BigDecimal.

The difference in the accuracy is best shown through an example. When performing multiplication of two numbers of the `double` type,

10*0.09 evaluates as 0.8999999999999999.

But when performing the same calculation using decimal arithmetic with the `BigDecimal` type,

10*0.09 evaluates as 0.9.

## How to use BigDecimal mode

Using JEP in BigDecimal mode is simple. Simply create a new JEP instance with:

    import com.singularsys.jep.bigDecimals.BigDecComponents;

    ...

    jep = new Jep(new BigDecComponents());

This initializes JEP with a special the BigDecNumberFactory, BigDecOperatorTable and BigDecFunctionTable. By default the math context is set to unlimited precision. But you can also initialize the components with a different math context. For example, to use 32-bit precision numbers simply use

    jep = new Jep(new BigDecComponents(MathContext.DECIMAL32));

For more information about MathContexts, refer to the Sun MathContext JavaDocs.

## Supported Operators and Functions

Guaranteeing precision unfortunately comes at the cost of more complex algorithms for basic operators and functions. For this reason, some of the functions and operators available for `double` arithmetic are not available in the BigDecimal mode.

The supported operators and functions are as follows:

+, -, *, /, ^ (power), % (modulus)

>, <, >=, <=, == (equals)

&& (and), || (or), ! (not)

Just like with JEP in standard mode, you can add your own custom functions.