Associative Array c'tor

[Bahman Movaqar via Digitalmars-d-learn]

On 07/11/2016 07:15 PM, Ali Çehreli wrote:
> Both AAs and slices behave like reference types even when passed by
> value: When a function adds an element, the argument sees that element
> as well. This is not the case when the argument is an empty (more
> correctly, null) AA or slice:
> 
> void foo(string[int] aa) {
>     aa[1] = "one";
> }
> 
> void main() {
>     string[int] a;
>     foo(a);
>     assert(a is null);
>     // The last result would be different if 'a' were not null
>     // before calling 'foo'.
> 
>     string[int] b;
>     b[0] = "zero";
>     foo(b);
>     assert(b[0] == "zero");
>     assert(b[1] == "one");
> }

Now I understand.
This is tricky --could introduce hard to find bugs.  Is there anyway to
make sure it doesn't happen?  Such as giving the AA a default empty
value on the declaration line --like `string[int] a = []`?

> P.P.S. There is std.algorithm.fold, which works with range chaining
> (unlike reduce, which was designed before ranges):
> 
>   https://dlang.org/phobos/std_algorithm_iteration.html#.fold

`fold` definitely feels more natural.

Thanks.

-- 
Bahman