blob: 7807512cc4d6cf101a469e020b66be3cd14a4d8d (
plain)
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
|
/*!
@file
Forward declares `boost::hana::take_while`.
@copyright Louis Dionne 2013-2016
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_TAKE_WHILE_HPP
#define BOOST_HANA_FWD_TAKE_WHILE_HPP
#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>
BOOST_HANA_NAMESPACE_BEGIN
//! Take elements from a sequence while the `predicate` is satisfied.
//! @ingroup group-Sequence
//!
//! Specifically, `take_while` returns a new sequence containing the
//! longest prefix of `xs` in which all the elements satisfy the given
//! predicate.
//!
//!
//! @param xs
//! The sequence to take elements from.
//!
//! @param predicate
//! A function called as `predicate(x)`, where `x` is an element of the
//! sequence, and returning a `Logical` representing whether `x` should be
//! included in the resulting sequence. In the current version of the
//! library, `predicate` has to return a `Constant Logical`.
//!
//!
//! Example
//! -------
//! @include example/take_while.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
constexpr auto take_while = [](auto&& xs, auto&& predicate) {
return tag-dispatched;
};
#else
template <typename S, typename = void>
struct take_while_impl : take_while_impl<S, when<true>> { };
struct take_while_t {
template <typename Xs, typename Pred>
constexpr auto operator()(Xs&& xs, Pred&& pred) const;
};
constexpr take_while_t take_while{};
#endif
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_FWD_TAKE_WHILE_HPP
|
