title: Compose path (with boost::filesystem)
body: <p>I have a file that describes input data, which is split into several other files. In my descriptor file, I first give the <strong>path A</strong> that tells where all the other files are found.</p>
  
  <p>The originator may set either a relative (to location of the descriptor file) or absolute path.</p>
  
  <p>When my program is called, the user gives the name of the descriptor file. It may not be in the current working directory, so the <strong>filename B</strong> given may also contain directories.</p>
  
  <p>For my program to always find the input files at the right places, I need to combine this information. If the path <strong>A</strong> given is absolute, I need to just that one. If it is relative, I need to concatenate it to the path <strong>B</strong> (i.e. directory portion of the filename).</p>
  
  <p>I thought <code>boost::filesystem::complete</code> may do the job for me. Unfortunately, it seems it is not. I also did not understand how to test wether a path given is absolute or not.</p>
  
  <p>Any ideas?</p>