//usage example: To list just Rascal source files,    Walk(|home:///workspace/|, ".rsc");
module Walk
import String;
import IO;
public void Walk(loc a, str pattern){
   for (entry <- listEntries(a))
      if (endsWith(entry, pattern))
         println(entry);
      elseif (isDirectory(a+entry))
         Walk(a+entry, pattern);
}