/** This is a solution to the Rosetta Code problem
    "Read a specific line from a file."
    https://rosettacode.org/wiki/Read_a_specific_line_from_a_file
*/
nthLine[filename, lineNum] :=
{
   line = nth[lines[filenameToURL[filename]], lineNum-1]
   if line != undef
      return line
   else
   {
      println["The file $filename does not contain a line number $lineNum"]
      return undef
   }
}