////
Copyright 2001-2004 Nicolai M. Josuttis
Copyright 2012 Marshall Clow
Copyright 2024 Christian Mazakas
Distributed under the Boost Software License, Version 1.0.
https://www.boost.org/LICENSE_1_0.txt
////

[#design]
# Design Rationale
:idprefix: design_
:cpp: C++

There was an important design tradeoff regarding the constructors: We could implement array as an "aggregate" (see Section 8.5.1, [dcl.init.aggr], of the C++ Standard). This would mean:

* An array can be initialized with a brace-enclosing, comma-separated list of initializers for the elements of the container, written in increasing subscript order:
+
--
```cpp
boost::array<int,4> a = { { 1, 2, 3 } };
```

Note that if there are fewer elements in the initializer list, then each remaining element gets default-initialized (thus, it has a defined value).
--

However, this approach has its drawbacks: **passing no initializer list means that the elements have an indetermined initial value**, because the rule says that aggregates may have:

* No user-declared constructors.
* No private or protected non-static data members.
* No base classes.
* No virtual functions.

Nevertheless, the current implementation uses this approach.

Note that for standard conforming compilers it is possible to use fewer braces (according to 8.5.1 (11) of the Standard). That is, you can initialize an array as follows:

```cpp
boost::array<int,4> a = { 1, 2, 3 };
```