Semantics of ^^

[bearophile]

Don:

> Based on everyone's comments, this is what I have come up with:

Looks good.


> * If y == 0,  x ^^ y is 1.
> * If both x and y are integers, and y > 0,  x^^y is equivalent to
>     { auto u = x; foreach(i; 1..y) { u *= x; } return u; }

You can rewrite both of those as:
{ typeof(x) u = 1; foreach (i; 0 .. y) { u *= x; } return u; }


> (1) Although the following special cases could be defined...
>   * If x == 1,  x ^^ y is 1
>   * If x == -1 and y is even, x^^y == 1
>   * If x == -1 and y is odd, x^^y == -1
> ... they are not sufficiently useful to justify the major increase in 
> complexity which they introduce.

This is not essential:
(-1)**n is a common enough shortcut to produce an alternating +1 -1, you can see it used often enough in Python code (and in mathematics). This search gives 433 results:
http://www.google.com/codesearch?q=\%28-1\%29\s*\*\*\s*[0-9a-zA-Z%28]+lang%3Apython
When used for this purpose (-1) is always compile time constant, so the compiler can grow a simple rule the rewrites:
(-1) ^^ n
as
(n & 1) ? -1 : 1

Bye,
bearophile