'in' for arrays?

[Bill Baxter]

Chris Nicholson-Sauls wrote:
> Lionello Lunesu wrote:
> 
>> Bill Baxter wrote:
>>
>>> I keep wanting to say
>>>   if (val in somearray) {
>>>   }
>>
>>
>> Wait! That's just it!
>>
>> It's "KEY in CONTAINER" and the KEY of a regular array is the index, 
>> not the value. So dare I suggest the following instead?
>>
>> if (index in somearray) {
>> }
>>
>> This "in" would be:
>> (cast(size_t)index < somearray.length?&somearray[index]:null)
>>
>> Totally analogous to the associative array. And it also solves the 
>> "Length comparison" issue.
>>
>> L.
> 
> 
> Now this I actually like... Can already think of places I could use it, 
> such as in Bovis during symbol/id lookups.  Its a nice idea.  (Might 
> just add it to Cashew in the meantime.)
> 
> -- Chris Nicholson-Sauls

Ugh.  I've created a monster.

That would make sense in Lua where there is only one data structure 
(table), which can be indexed with numbers or non-numbers equally well, 
but in D, it just doesn't seem right to say 2 is 'in' 
["spam","eggs","spam"].  I certainly don't see any 2 in there.  The 
operation you want seems more like a get():

    T* get(T[] arr, size_t index) {
       return (index < arr.length ? &arr[index] : null)
    }

    if (somearray.get(10)) {
    }

The dict type in Python uses something like that for safe indexing, 
otherwise you use [] if throwing an exception is ok.

--bb