Help with specific template function

[Vladimirs Nordholm]

Hello Dlang community!

I need help in creating a template function which would look like 
the following pseudo-code:

     void foo(<a number>, <also a number>, <required arg>, 
<optional arg>...);
     // would be used as `void foo(x, y, arg1, arg2, ..., argN)`

     // valid examples:
     foo(5.332, 1, "a string", 123, "42");
     foo(3, 44, false);

     // invalid examples:
     foo(1, 1);
     foo(3, "stringers", "arg");

The underlying problems are:
* How do I ensure the two first arguments (used as coordinates) 
are types of numbers (all kinds: ints, floats, reals, etc.)
* At least one argument is passed after the coordinates

Best regards,
Vladimris Nordholm