libmuparser-doc 2.2.3-6 / usr / share / doc / libmuparser-doc / html / sources / mup_version.html

<!-- 
//
//
//  
//   Example code
//
//
//
-->

<h2><a id="idExample"></a>Example code</h2>

<p>
If you put all this together, you get the source code for a small application. The application defines a parser variables ("<code>a</code>") and adds 
a user defined functions named "<code>MyFunc</code>". When using the parser make sure that you don't forget to catch the <code>Parser::exception_type</code> in your application. It contains detailed information helping you to find syntax errors in your formula.
</p>

<pre>
<span class="code_pp">#include &lt;iostream&gt;</span>
<span class="code_pp">#include "muParser.h"</span>

<span class="code_cmt">// Function callback</span>
<span class="code_kw">double</span> MySqr(<span class="code_kw">double</span> a_fVal) 
{ 
  <span class="code_kw">return</span> a_fVal*a_fVal; 
}

<span class="code_cmt">// main program</span>
<span class="code_kw">int</span> main(<span class="code_kw">int</span> argc, <span class="code_kw">char</span>* argv[])
{
  <span class="code_kw">using namespace</span> mu;

  <span class="code_kw">try</span>
  {
    <span class="code_kw">double</span> fVal = <span class="code_digit">1</span>;
    <span class="code_kw_lib">Parser</span> p;
    <span class="code_kw_lib">p.DefineVar</span>(<span class="code_str">"a"</span>, &amp;fVal); 
    <span class="code_kw_lib">p.DefineFun</span>(<span class="code_str">"MySqr"</span>, MySqr); 
    <span class="code_kw_lib">p.SetExpr</span>(<span class="code_str">"MySqr(a)*_pi+min(10,a)"</span>);

    <span class="code_kw">for</span> (std::size_t a=<span class="code_digit">0</span>; a<100; ++a)
    {
      fVal = a;  <span class="code_cmt">// Change value of variable a</span>
      std::cout &lt;&lt; <span class="code_kw_lib">p.Eval()</span> &lt;&lt; std::endl;
    }
  }
  <span class="code_kw">catch</span> (<span class="code_kw_lib">Parser::exception_type</span> &amp;e)
  {
    std::cout &lt;&lt; <span class="code_kw_lib">e.GetMsg()</span> &lt;&lt; std::endl;
  }
  <span class="code_kw">return</span> <span class="code_digit">0</span>;
}
</pre>


<!-- 
//
//
//
//  Benchmarks
//
//
//
-->

<hr/>
<h2><a id="idBench"></a>Benchmarks</h2>

<p>
Finally, I'd like to give you some benchmarks. The benchmarking was done on an Intel 
Pentium P-4 with 2.6 GHz, with a version compiled by using MSVC++ 7.1 (Standard edition).
The diagram shows number of <b>evaluations per seconds vs. expression length</b>. 
I compared both the static lib and the dll version with two other parsers that are freely available 
on the net, very fast and have a similar set of features. One of them is a commercial product.
</p>

<p>
  <img src="images/bench2.jpg" alt="parser benchmarks" border="0" height="489" width="560"/>
</p>

<p>
A higher curve means better performance. Expressions were created randomly. They used only <code>sin</code> and <code>cos</code> functions and contained 
multiple variables and constants. In order to smoothen the curves each point represents the value of a
running average over 10 sample expressions. 
</p>