Extending arithmetic

[Per Bergqvist]

> Strong typing would certainly make it easier on the compiler.       
Extending                                                             
> arithmetic to tuples shouldn't place that big a burden on the       
compiler.                                                             
>   The tuples would need to have all numeric elements, and it might  
be a                                                                  
> good idea to have a flag identifing a tuple as strictly numeric.    
Internally maybe, as a performance improvement, but certainly not     
accessible for the programmer.                                        
                                                                      
/Per