1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
|
/*!
@file
Forward declares `boost::hana::concat`.
@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)
*/
#ifndef BOOST_HANA_FWD_CONCAT_HPP
#define BOOST_HANA_FWD_CONCAT_HPP
#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>
BOOST_HANA_NAMESPACE_BEGIN
//! Combine two monadic structures together.
//! @ingroup group-MonadPlus
//!
//! Given two monadic structures, `concat` combines them together and
//! returns a new monadic structure. The exact definition of `concat`
//! will depend on the exact model of MonadPlus at hand, but for
//! sequences it corresponds intuitively to simple concatenation.
//!
//! Also note that combination is not required to be commutative.
//! In other words, there is no requirement that
//! @code
//! concat(xs, ys) == concat(ys, xs)
//! @endcode
//! and indeed it does not hold in general.
//!
//!
//! Signature
//! ---------
//! Given a `MonadPlus` `M`, the signature of `concat` is
//! @f$ \mathtt{concat} : M(T) \times M(T) \to M(T) @f$.
//!
//! @param xs, ys
//! Two monadic structures to combine together.
//!
//!
//! Example
//! -------
//! @include example/concat.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
constexpr auto concat = [](auto&& xs, auto&& ys) {
return tag-dispatched;
};
#else
template <typename M, typename = void>
struct concat_impl : concat_impl<M, when<true>> { };
struct concat_t {
template <typename Xs, typename Ys>
constexpr auto operator()(Xs&& xs, Ys&& ys) const;
};
constexpr concat_t concat{};
#endif
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_FWD_CONCAT_HPP
|
