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<html><!-- #BeginTemplate "/Templates/maintemplate.dwt" -->
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<title>JEP - Java Math Expression Parser</title>
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<li><a href="../javadoc/index.html" target="_blank">JavaDoc <img src="img/new-window-icon.gif" width="15" height="11"></a></li>
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<h1>JEP</h1>
<ul>
<li><a href="index.html">Basic Usage</a></li>
<li><a href="variables.html">Variables</a></li>
<li><a href="types.html">Data types</a></li>
<li><a href="operators.html">Operators</a></li>
<li><a href="functions.html">Functions</a></li>
<li><a href="advanced.html">Advanced Features</a></li>
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<h1>Extensions</h1>
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<li><a href="extensions/index.html">Overview</a></li>
<li><a href="extensions/xjep.html">XJep</a></li>
<li><a href="extensions/djep.html">Differentiation</a></li>
<li><a href="extensions/vectorjep.html">Vectors and Matrices</a></li>
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<h1><a name="top"></a>Basic Usage</h1>
<ul>
<li><a href="#gettingstarted">Getting started</a></li>
<li><a href="#errorhandling">Error handling</a></li>
<li><a href="#evaluatingexpressions">Evaluating expressions</a></li>
<li><a href="#alternate">Alternate parsing and evaluation functions</a></li>
<li><a href="#implicitmul">Implicit multiplication</a></li>
</ul>
<h2><a name="gettingstarted"></a>Getting started</h2>
<p>Using the JEP package of classes in your project is simple! The following
steps will get you started quickly.</p>
<ol>
<li>Download the JEP package</li>
<li>Unpack the archive</li>
<li>Move the jep-x.x.x.jar file to a directory of your choice (optional)</li>
<li>IMPORTANT: For the Java compiler to be able to find the JEP classes when
compiling your program, it needs to know their location. So you will need
to add the location of the .jar file to your CLASSPATH environment variable
(if you don't know how, <a href="http://java.sun.com/j2se/1.5.0/docs/tooldocs/windows/classpath.html" target="_blank">read
this</a>). Your CLASSPATH variable should contain something like C:\java\packages\jep-x.x.x.jar,
depending on where you place the jar file. Alternatively you may need to
set the location of the jar archive in your Java IDE so that the compiler
finds the library.</li>
<li>In your program, create a new parser object with
<pre>org.nfunk.jep.JEP myParser = new org.nfunk.jep.<a href="../javadoc/org/nfunk/jep/JEP.html" target="_blank">JEP</a>();</pre>
</li>
<li>Add the standard functions and constants if you want to be able to evaluate
expressions with trigonometric functions and the constants <i>pi</i> and
<i>e</i>.
<pre>myParser.<a href="../javadoc/org/nfunk/jep/JEP.html#addStandardFunctions()" target="_blank">addStandardFunctions()</a>;
myParser.<a href="../javadoc/org/nfunk/jep/JEP.html#addStandardConstants()" target="_blank">addStandardConstants()</a>;</pre>
</li>
<li> By default you need to specify which variables can be used in the expression.
If a variable is not added before the expression is parsed, the parser will
claim that the expression is invalid (this can be changed by <a href="variables.html#allowingundeclared">allowing
undeclared variables</a>).<br>
To add the variable <i>x</i> and initialize it to 0 for example, write
<pre>myParser.<a href="../javadoc/org/nfunk/jep/JEP.html#addVariable(java.lang.String, double)" target="_blank">addVariable("x", 0)</a>;</pre>
</li>
<li>Parse the expression, and evaluate it:
<pre>myParser.<a href="../javadoc/org/nfunk/jep/JEP.html#parseExpression(java.lang.String)" target="_blank">parseExpression(ExpressionString)</a>;
result = myParser.<a href="../javadoc/org/nfunk/jep/JEP.html#getValue()" target="_blank">getValue()</a>;</pre>
</li>
<li> The values of variables can be changed with the <a href="../javadoc/org/nfunk/jep/JEP.html#addVariable(java.lang.String, double)" target="_blank">addVariable(String,
double)</a> method.<br>
</li>
</ol>
<p>The code of the sample applets provide more extensive look at how the parser
methods are used.</p>
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<h2><a name="errorhandling"></a>Error handling</h2>
<p>Errors can occur both while parsing an expression and while evaluating an
expression. The <a href="../javadoc/org/nfunk/jep/JEP.html#hasError()" target="_blank">hasError()</a>
method reports whether an error has occurred during the most recent action
(either parsing or evaluation). If the result is <code>true</code>, you can
then use <a href="../javadoc/org/nfunk/jep/JEP.html#getErrorInfo()" target="_blank">getErrorInfo()</a>
to obtain further information on the errors that have occurred.</p>
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<h2><a name="evaluatingexpressions"></a>Evaluating expressions</h2>
<p>Four methods for evaluating an expression are available:</p>
<ul>
<li><a href="../javadoc/org/nfunk/jep/JEP.html#getValue()" target="_blank">getValue()</a>:
Use this if you are expecting a normal floating point value.</li>
<li><a href="../javadoc/org/nfunk/jep/JEP.html#getComplexValue()" target="_blank">getComplexValue()</a>:
Use this if you are expecting a complex value.</li>
<li><a href="../javadoc/org/nfunk/jep/JEP.html#getValueAsObject()" target="_blank">getValueAsObject()</a>:
Returns the result as an Object (any type)</li>
<li><a href="../javadoc/org/nfunk/jep/JEP.html#evaluate(org.nfunk.jep.Node)" target="_blank">evaluate(Node
root)</a>: Evaluates a tree with from a root node and returns the result
as an Object.</li>
</ul>
<p>The first two methods call <a href="../javadoc/org/nfunk/jep/JEP.html#getValueAsObject()" target="_blank">getValueAsObject()</a>
internally, and perform the necessary conversions into either a <code>double</code>
value, or a <code>Complex</code> object. </p>
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<h2><a name="alternate"></a>Alternate parsing and evaluation functions</h2>
<p>There is an alternative method to parsing and evaluating expression which
allows a little more flexibility in applications especially when working with
a set of related equations. These are: </p>
<pre>public Node <a href="../javadoc/org/nfunk/jep/JEP.html#parse(java.lang.String)">parse(String expression)</a> throws ParseException<br>public Object <a href="../javadoc/org/nfunk/jep/JEP.html#evaluate(org.nfunk.jep.Node)">evaluate(Node node)</a> throws Exception</pre>
which parse and evaluate the expression. These can be used like
<pre>try<br>{<br> // Alternative syntax<br> Node node1 = j.parse("z=i*pi");<br> j.evaluate(node1);<br> Node node2 = j.parse("exp(z)");<br> Object val2 = j.evaluate(node2);<br> System.out.println("Value: "+val2);<br>}<br>catch(ParseException e) {<br> System.out.println("Error with parsing");<br>}<br>catch(Exception e) {<br> System.out.println("Error with evaluation");<br>}</pre>
<p>Hence its a bit easier to keep track of a number of equations. Note that
using this syntax Exceptions need to be caught and the <a href="../javadoc/org/nfunk/jep/JEP.html#getTopNode()">getTopNode()</a>
method will not return meaningful results.</p>
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<h2><a name="implicitmul"></a>Implicit multiplication</h2>
<p>You can enable the implicit multiplication option with <a href="../javadoc/org/nfunk/jep/JEP.html#setImplicitMul(boolean)" target="_blank">setImplicitMul(true)</a>.
The default setting is false (no implicit multiplication).</p>
<p>Implicit multiplication allows expressions such as "2 x" to be
interpreted as "2*x". Note that a space is required between two
variables for them to be interpreted as being multiplied. The same holds for
a variable followed by a number. For example "y 3" is interpreted
as "y*3", but "y3" is interpreted as a single variable
with the name y3. If a variable is preceded by a number, no space is required
between them for implicit multiplication to come in effect.</p>
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