/*! @file Forward declares `boost::hana::intersperse`. @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_INTERSPERSE_HPP #define BOOST_HANA_FWD_INTERSPERSE_HPP #include <boost/hana/config.hpp> #include <boost/hana/core/when.hpp> BOOST_HANA_NAMESPACE_BEGIN //! Insert a value between each pair of elements in a finite sequence. //! @ingroup group-Sequence //! //! Given a finite `Sequence` `xs` with a linearization of //! `[x1, x2, ..., xn]`, `intersperse(xs, z)` is a new sequence with a //! linearization of `[x1, z, x2, z, x3, ..., xn-1, z, xn]`. In other //! words, it inserts the `z` element between every pair of elements of //! the original sequence. If the sequence is empty or has a single //! element, `intersperse` returns the sequence as-is. In all cases, //! the sequence must be finite. //! //! //! @param xs //! The sequence in which a value is interspersed. //! //! @param z //! The value to be inserted between every pair of elements of the sequence. //! //! //! Example //! ------- //! @include example/intersperse.cpp #ifdef BOOST_HANA_DOXYGEN_INVOKED constexpr auto intersperse = [](auto&& xs, auto&& z) { return tag-dispatched; }; #else template <typename S, typename = void> struct intersperse_impl : intersperse_impl<S, when<true>> { }; struct intersperse_t { template <typename Xs, typename Z> constexpr auto operator()(Xs&& xs, Z&& z) const; }; constexpr intersperse_t intersperse{}; #endif BOOST_HANA_NAMESPACE_END #endif // !BOOST_HANA_FWD_INTERSPERSE_HPP