<p>
  Since LTPDA is an object-oriented system, the user must create objects of different
  types using the appropriate constructors. The various constructor forms for each 
  different LTPDA class can be explored using the <it>constructor helper</it>.
</p>
<p>
  To start the constructor helper GUI:
</p>
<div class="fragment"><pre>
    >> ltpda_constructor_helper
</pre></div>
<p>
  or click the appropriate button on the Launch Bay.
</p>
<p>
  You should then be presented with the following figure:
</p>
<br>
<img src="images/constructor_helper.png" alt="LTPDA Constructor Helper" border="3">
<br>
<br>
<p>
  Selecting a class from the drop-down list reveals the possible parameter sets for that 
  class constructor. Selecting a parameter set reveals the default parameter list constructor
  string for constructing that class object in this way. For example, if we want to construct
  and Analysis Object using the time-series constructor, select the AO class then click on 
  "From Time-series Function". You should then see:
</p>
<br>
<img src="images/constructor_helper_eg1.png" alt="LTPDA Constructor Helper" border="3">
<br>
<br>
<p>
  You can then edit the parameter list and build the object by clicking on <tt>Build</tt>. 
</p>