forked from boostorg/array
40 lines
1.4 KiB
Plaintext
40 lines
1.4 KiB
Plaintext
////
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Copyright 2001-2004 Nicolai M. Josuttis
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Copyright 2012 Marshall Clow
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Copyright 2024 Christian Mazakas
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Distributed under the Boost Software License, Version 1.0.
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https://www.boost.org/LICENSE_1_0.txt
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////
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[#design]
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# Design Rationale
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:idprefix: design_
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:cpp: C++
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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:
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* 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:
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+
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--
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```cpp
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boost::array<int,4> a = { { 1, 2, 3 } };
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```
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Note that if there are fewer elements in the initializer list, then each remaining element gets default-initialized (thus, it has a defined value).
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--
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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:
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* No user-declared constructors.
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* No private or protected non-static data members.
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* No base classes.
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* No virtual functions.
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Nevertheless, the current implementation uses this approach.
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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:
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```cpp
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boost::array<int,4> a = { 1, 2, 3 };
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```
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