> It turns out that the both pair_id's never match and the loop breaks with: > > >>Trying to access an element behind the last one! > << This assertion is in the operator[]/value(str, pos) function for the String class. Did you try to run the program within a debugger to see where the problem occurs in your program? Please provide a complete, compiling problem and a minimal SAM file (should be 2 lines after the header, right?) that allow us to reproduce the problem. Bests, Manuel