variable existence checking

[A.V.Kuznetsov]

Hi,

> 
> I would actually prefer an existence operator, but NOT !!. This has a definite
> meaning: "is true" (in macro !!x is equivalent to x!=0). I have been thinking
> along the lines of an "exists" operator "??" instead:

You are right as always. 
 
>     ??var: return true (1) if var has a value, false (0) otherwise
>     ??array[]: return true if array is an array
>     ??array[key]: return (key in array)
>     ??array[key1][key2]: return ((key1 in array) && (key2 in array))
> (with my array.key language extension, also: array??.key)
> 

??array[key1][key2]: return ((key1 in array) && (key2 in array[key1]))

Alexey