mapping implemented in functions vs in structures

[HP Wei]

>But why not:
>
>map_el(m1, m2, x1) -> y1;
>map_el(m1, m2, x2) -> y2;
>...
> or
>
>map_el({m1, m2}, x1) -> y1;
>map_el({m1, m2}, x2) -> y2;

  Oh, yeah!!!  This is much SIMPLER and clear.
  
  Thanks a lot.
--hp