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<title>JEP - Java Math Expression Parser</title>
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<h1>JEP</h1>
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<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>
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<h1><a name="top"></a>Data Types</h1>
<p>JEP supports a number of different data types and allows. These include numbers,
<a href="#strings">strings</a>, <a href="#vectors">vectors</a>, <a href="#complexnumbers">complex
numbers</a>. Numbers are represented by the <code>double</code> data type
by default. It is however possible to change the internal representation as
described in the section <a href="#usingcustomnumberclasses">Using custom
number classes</a>.</p>
<h2><a name="strings"></a>Strings</h2>
<p>Strings can be entered in an expression by using double quotes. They can
be concatenated with the + operator and compared with the == and != relational
operators. A sample expression involving the string type is "foo"
+ "bar" == "foobar", which would be evaluated by JEP as
1 (true).</p>
<p>To add a string as a variable, use the <a href="../javadoc/org/nfunk/jep/JEP.html#addVariable(java.lang.String, java.lang.Object)" target="_blank">addVariable(String
name, Object value)</a> method. If the result of an expression is a string,
it can be obtained by calling the <a href="../javadoc/org/nfunk/jep/JEP.html#getValueAsObject()" target="_blank">getValueAsObject()</a>
function.</p>
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<h2><a name="vectors"></a>Vectors</h2>
<p>Vectors are ordered sets of Double elements. A vector is a list of values,
separated by commas, and enclosed by square brackets. An example expression
involving a vector is:
<pre>[3, 4, 5]*2</pre>
<p>It would be evaluated as [6, 8, 10] by JEP. To add a vector as variable,
use the <a href="../javadoc/org/nfunk/jep/JEP.html#addVariable(java.lang.String, java.lang.Object)" target="_blank">addVariable(String
name, Object value)</a> method. If the result of an expression is a vector,
it can be obtained by calling the <a href="../javadoc/org/nfunk/jep/JEP.html#getValueAsObject()" target="_blank">getValueAsObject()</a>
function.</p>
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<h2><a name="complexnumbers"></a>Complex numbers</h2>
<p>If you want to use complex numbers in your expression, you can call <a href="../javadoc/org/nfunk/jep/JEP.html#addComplex()" target="_blank">addComplex()</a>
after creating the parser object. This will add the imaginary unit as constant<b>
</b><i>i</i>. Two parser functions re() and im() are also added and can be
used to obtain the real and imaginary components of complex numbers. You will
need to import the <a href="../javadoc/org/nfunk/jep/type/Complex.html" target="_blank">org.nfunk.jep.type.Complex</a>
class to be able to manipulate complex values from expressions.</p>
<p>By using the imaginary unit constant <i>i</i>, you can work with complex
numbers in your expressions. A sample complex expression would be (1+2*i)^3.
Currently the (re, IM) notation is not supported.</p>
<p>To obtain a complex value from an expression, you must use the <a href="../javadoc/org/nfunk/jep/JEP.html#getComplexValue()" target="_blank">getComplexValue()</a>
function. It will evaluate the expression and return the result as a Complex
object. Note that the class used internally for Complex numbers is also used
for returning the value.</p>
<p>Adding a complex variable or constant to the parser before evaluating an
expression can be done with <a href="../javadoc/org/nfunk/jep/JEP.html#addVariable(java.lang.String, double, double)" target="_blank">addVariable(String
name, double re, double IM)</a>. It takes three parameters: the name of the
variable as string, the real component, and the imaginary component.</p>
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<h2><a name="usingcustomnumberclasses"></a>Using custom number classes</h2>
<p>By default when an expression such as "1+2" is parsed, the constants
"1" and "2" are created internally as Double objects.
In most cases this is fine, but in some cases you may want to use custom classes
for representing numbers.</p>
<p>This is made possible through creating a number class that implements the
<a href="../javadoc/org/nfunk/jep/type/NumberFactory.html" target="_blank">NumberFactory</a>
interface. It includes one method called <a href="../javadoc/org/nfunk/jep/type/NumberFactory.html#createNumber(java.lang.String)" target="_blank">createNumber(String
value)</a>, which should return an object initialized to the value of the
parameter. You can load your custom number factory with the JEP constructor
<code>JEP(boolean traverse_in, Boolean allowUndeclared_in, Boolean implicitMul_in,
NumberFactory numberFactory_in)</code>.</p>
<p>The custom number objects need to be handled by custom functions which you
can create by following the instructions on the <a href="functions.html#custom">Custom
Functions</a> page.</p>
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<h2><a name="customtypes"></a>Custom types</h2>
<p>In most cases, you will only need to work with the few built in types that
JEP supplies (Double, Complex, Vector, String). But suppose you want to evaluate
expressions that involve other types. This is possible by using the <a href="../javadoc/org/nfunk/jep/JEP.html#addVariable(java.lang.String, java.lang.Object)" target="_blank">addVariableAsObject(String
name, Object value)</a> method to add variables of any type. The only place
where the type of a variable matters, is in the function classes.</p>
<p>When an expression is evaluated, values are operated on with the classes
in the function package. These include the operators (such as <a href="../javadoc/org/nfunk/jep/function/Add.html" target="_blank">Add</a>
and <a href="../javadoc/org/nfunk/jep/function/Subtract.html" target="_blank">Subtract</a>),
as well as the functions (such as <a href="../javadoc/org/nfunk/jep/function/Sine.html" target="_blank">Sine</a>
and <a href="../javadoc/org/nfunk/jep/function/Cosine.html" target="_blank">Cosine</a>).
Without making modifications to the source code, only the default types are
handled with these classes. So, in order to be able to handle your own types,
you will need to modify theses classes, or make your own function classes
as described in the custom functions section.</p>
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