Boost.Hana  1.7.1
Your standard library for metaprogramming
std::array< T, N > Struct Template Reference

Description

template<typename T, std::size_t N>
struct std::array< T, N >

Adaptation of std::array for Hana.

Modeled concepts

  1. Comparable
    std::arrays are compared as per std::equal, except that two arrays with different sizes compare unequal instead of triggering an error and the result of the comparison is constexpr if both arrays are constexpr.
    // Copyright Louis Dionne 2013-2017
    // Distributed under the Boost Software License, Version 1.0.
    // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
    #include <array>
    namespace hana = boost::hana;
    constexpr std::array<int, 4> xs = {{1, 2, 3, 4}};
    constexpr std::array<int, 5> ys = {{1, 2, 3, 4, 5}};
    // arrays have different constexpr contents; result is a constexpr bool
    static_assert(hana::equal(xs, xs), "");
    // arrays have different lengths; result is an integral_constant
    int main() { }
    Defines macros to perform different kinds of assertions.
    Defines boost::hana::equal.
    Adapts std::array for use with Hana.
    constexpr auto equal
    Returns a Logical representing whether x is equal to y.
    Definition: equal.hpp:64
    constexpr auto not_equal
    Returns a Logical representing whether x is not equal to y.
    Definition: not_equal.hpp:54
    #define BOOST_HANA_CONSTANT_CHECK(...)
    Equivalent to BOOST_HANA_CONSTANT_ASSERT, but not influenced by the BOOST_HANA_CONFIG_DISABLE_ASSERTI...
    Definition: assert.hpp:239
    Namespace containing everything in the library.
    Definition: accessors.hpp:20
    Defines boost::hana::not_equal.
    Adaptation of std::array for Hana.
    Definition: array.hpp:64
  2. Orderable
    std::arrays are ordered with the usual lexicographical ordering, except that two arrays with different size can be ordered instead of triggering an error and the result of the comparison is constexpr if both arrays are constexpr.
    // Copyright Louis Dionne 2013-2017
    // Distributed under the Boost Software License, Version 1.0.
    // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
    #include <array>
    namespace hana = boost::hana;
    constexpr std::array<int, 4> evens = {{2, 4, 6, 8}};
    constexpr std::array<int, 4> odds = {{1, 3, 5, 7}};
    constexpr std::array<int, 5> up_to_5 = {{1, 2, 3, 4, 5}};
    // arrays with same length
    static_assert(hana::less(odds, evens), "");
    // arrays with different lengths
    static_assert(hana::less(up_to_5, odds), "");
    int main() { }
    constexpr auto less
    Returns a Logical representing whether x is less than y.
    Definition: less.hpp:37
    Defines boost::hana::less.
  3. Foldable
    Folding an array from the left is equivalent to calling std::accumulate on it, except it can be constexpr.
    // Copyright Louis Dionne 2013-2017
    // Distributed under the Boost Software License, Version 1.0.
    // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
    #include <array>
    namespace hana = boost::hana;
    int main() {
    std::array<int, 5> a = {{0, 1, 2, 3, 4}};
    auto b = hana::unpack(a, [](auto ...i) {
    return std::array<int, sizeof...(i)>{{(i + 10)...}};
    });
    BOOST_HANA_RUNTIME_CHECK(b == std::array<int, 5>{{10, 11, 12, 13, 14}});
    }
    constexpr auto unpack
    Invoke a function with the elements of a Foldable as arguments.
    Definition: unpack.hpp:79
    #define BOOST_HANA_RUNTIME_CHECK(...)
    Equivalent to BOOST_HANA_RUNTIME_ASSERT, but not influenced by the BOOST_HANA_CONFIG_DISABLE_ASSERTIO...
    Definition: assert.hpp:209
    Defines boost::hana::unpack.
  4. Iterable
    Iterating over a std::array is equivalent to iterating over it with a normal for loop.
    // Copyright Louis Dionne 2013-2017
    // Distributed under the Boost Software License, Version 1.0.
    // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
    #include <array>
    namespace hana = boost::hana;
    constexpr std::array<int, 5> a = {{0, 1, 2, 3, 4}};
    static_assert(hana::at_c<2>(a) == 2, "");
    static_assert(hana::equal(hana::drop_front(a), std::array<int, 4>{{1, 2, 3, 4}}), "");
    int main() { }
    Defines boost::hana::at and boost::hana::at_c.
    Defines boost::hana::drop_front.
    constexpr auto drop_front
    Drop the first n elements of an iterable, and return the rest.
    Definition: drop_front.hpp:47