mep4j Files

Math Expression Parser 4 Java

MEP4J is a high performance math expression strings parser for Java.

The library manages the 5 operators (+, -, /, %, *) together with the following functions:
- "abs"
- "cos"
- "sin"
- "acos"
- "asin"
- "cosh"
- "sinh"
- "tan",
- "tanh"
- "atan"
- "sqrt"
- "cbrt"
- "root"
- "log"
- "log10"
- "log1p"
- "exp"
- "expm1"
- "atan2"
- "pow"

The library supports variables (case insensitive), custom and pre-loaded ("e" and "pi").


Usage examples:

1. No Variables

import net.sourceforge.mep4j.core.MathParser;
import net.sourceforge.mep4j.core.MathParserException;

...

double myRes1 = new MathParser().parse("2 * 4 - 5").execute();


2. With Variables

import net.sourceforge.mep4j.core.MathParser;
import net.sourceforge.mep4j.core.MathParserException;

...

double myRes1 = new MathParser().addVariable("S", 2.0).parse("s * 4 - 21").execute();


3. Multiple executions (changing variable values)

import net.sourceforge.mep4j.core.MathParser;
import net.sourceforge.mep4j.core.MathParserException;

...

int num_variations = 100;
int init_value = 10;
MathParser mathParser = new MathParser();
mathParser.addVariable("x", init_value);
mathParser.parse("2 + (7 - 5) * 3.14159 * pow(x, (12-10)) + sin(-3.141)");
for(int i = init_value; i < num_variations; ++i) {
	Double result = mathParser.execute();
	mathParser.addVariable("x", i);
}


Methods:

Class "MathParser"

- String getVersion() - Static

Returns the version description

- MathParser() - Constructor

Instantiates the object

- MathParser addVariable(String varName, Long longValue)

Adds the value (name - Long value) to the parser and returns the MathParser object

- MathParser addVariable(String varName, Double doubleValue)

Adds the value (name - Double value) to the parser

- Double getVariable(String varName)

Returns the value (Double value) previously set to the parser or NULL

- MathParser parse(String mathExpression)

Parse the math expression to execute and returns the MathParser object.
If the expression contains variables this method must be called after the "addVariable" method.

- Double execute()

Execute the expression previously parsed with the "parse(String)" method.
If errors happened the method returns the "Double.Nan" value.

- MathParserException getLastException()

If the "execute()" method returns the "Double.Nan" value than this method will return the 
exception that describes what was wrong in the last "execute()" or "parse(String)" method call.