title: Can anyone point to a tutorial of adding new functions in ddmathparser?
body: <p>I am new to programming. I want to add some new functions such as derivatives and integrations to <code>ddmathparser</code>. The only one I can find is the short tutorial on <code>ddmathparser</code>'s wiki page <a href="https://github.com/davedelong/DDMathParser/wiki/Adding-New-Functions" rel="nofollow">https://github.com/davedelong/DDMathParser/wiki/Adding-New-Functions</a> . However, I can't follow it because it's too short and after reading it several times, I still can't understand what it's doing. So can anyone elaborate steps to add a new function or give me some more detailed tutorials of doing this? 
  I really did my research but I can't find one. Thanks very much. </p>