'in' for arrays?

[Bill Baxter]

I keep wanting to say
   if (val in somearray) {
   }

but 'in' doesn't work for arrays...  Is there any reason why not?
Basically I just expect it to do something like this function (untested, 
modified from a similar function in Cashew):

T* item_in (T) (T[] haystack, T cmp)
{
   foreach (index, inout needle; haystack) {
     if (needle==cmp) {
       return &needle;
     }
   }
   return null;
}

I.e. I just expect it to do a plain old linear search through the list, 
nothing fancy, but it would be handy.

--bb