Referring to array element by descriptive name

[albert-j via Digitalmars-d-learn]

Is it possible to refer to an array element by a descriptive 
name, just for code clarity, without performance overhead? E.g.

void aFunction(double[] arr) {
     double importantElement = arr[3];
     ... use importantElement ...
}

But the above, I suppose, introduces an extra copy operation?