How to check if script belongs to first note

[Martín Rincón Botero]

     Hi all,  

  
I hope this can be answered with pseudo- C++ code. I've been working on 
something but I'm stuck with this. Say I have a list of scripts produced by 
extract_grob_set. They all make part of a spanner. How can I generally check if 
a certain script is attached to the first note of the spanner? I tried getting 
the x parent of the script (which I imagine is a note), getting the column of 
this x parent (with get_column ()), and then comparing that column with the 
first note-column of the spanner without success. Can someone point me in the 
right direction?
  

  
—Martín.