Which reminds me of an insightful observation that the array indexing operator [] and the function call operator () are basically doing the same thing: evaluating a function and returning a value.

So what you've just described is basically Currying, or partial function evaluation. It's a bit like defining "al(i)" as array lookup for an index 'i' instead of "[i]". Then the following are equivalent:

    something[i][j]
    something.al(i).al(j)

What people also want are:

    something[i,j]
    something.al(i,j)

In languages like Haskell, every function can always be evaluated argument-by-argument, with no special effort by the programmer. The compiler takes care of generating the code for the various intermediate call forms. In languages like C++, it would be a significant hassle to create all of the various partially-evaluated wrapper types.