zip.hpp
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/*!
@file
Forward declares `boost::hana::zip`.
Copyright Louis Dionne 2013-2022
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_ZIP_HPP
#define BOOST_HANA_FWD_ZIP_HPP
#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>
namespace boost { namespace hana {
//! Zip one sequence or more.
//! @ingroup group-Sequence
//!
//! Given `n` sequences `s1, ..., sn`, `zip` produces a sequence whose
//! `i`-th element is a tuple of `(s1[i], ..., sn[i])`, where `sk[i]`
//! denotes the `i`-th element of the `k`-th sequence. In other words,
//! `zip` produces a sequence of the form
//! @code
//! [
//! make_tuple(s1[0], ..., sn[0]),
//! make_tuple(s1[1], ..., sn[1]),
//! ...
//! make_tuple(s1[M], ..., sn[M])
//! ]
//! @endcode
//! where `M` is the length of the sequences, which are all assumed to
//! have the same length. Assuming the sequences to all have the same size
//! allows the library to perform some optimizations. To zip sequences
//! that may have different lengths, `zip_shortest` should be used
//! instead. Also note that it is an error to provide no sequence at all,
//! i.e. `zip` expects at least one sequence.
//!
//!
//! Example
//! -------
//! @include example/zip.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
constexpr auto zip = [](auto&& x1, ..., auto&& xn) {
return tag-dispatched;
};
#else
template <typename S, typename = void>
struct zip_impl : zip_impl<S, when<true>> { };
struct zip_t {
template <typename Xs, typename ...Ys>
constexpr auto operator()(Xs&& xs, Ys&& ...ys) const;
};
BOOST_HANA_INLINE_VARIABLE constexpr zip_t zip{};
#endif
}} // end namespace boost::hana
#endif // !BOOST_HANA_FWD_ZIP_HPP