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/*!
@file
Forward declares `boost::hana::remove_if`.
@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_REMOVE_IF_HPP
#define BOOST_HANA_FWD_REMOVE_IF_HPP
#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>
BOOST_HANA_NAMESPACE_BEGIN
//! Remove all the elements of a monadic structure that satisfy some
//! predicate.
//! @ingroup group-MonadPlus
//!
//! Given a monadic structure `xs` and a unary predicate, `remove_if`
//! returns a new monadic structure equal to `xs` without all its elements
//! that satisfy the predicate. This is equivalent to `filter` with a
//! negated predicate, i.e.
//! @code
//! remove_if(xs, predicate) == filter(xs, negated predicated)
//! @endcode
//!
//!
//! Signature
//! ---------
//! Given a MonadPlus `M` and a predicate of type \f$ T \to Bool \f$ for
//! some compile-time Logical `Bool`, the signature is
//! \f$
//! \mathrm{remove\_if} : M(T) \times (T \to Bool) \to M(T)
//! \f$
//!
//! @param xs
//! A monadic structure to remove some elements from.
//!
//! @param predicate
//! A unary predicate called as `predicate(x)`, where `x` is an element
//! of the structure, and returning whether `x` should be removed from
//! the structure. In the current version of the library, `predicate`
//! must return a compile-time Logical.
//!
//!
//! Example
//! -------
//! @include example/remove_if.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
constexpr auto remove_if = [](auto&& xs, auto&& predicate) {
return tag-dispatched;
};
#else
template <typename M, typename = void>
struct remove_if_impl : remove_if_impl<M, when<true>> { };
struct remove_if_t {
template <typename Xs, typename Pred>
constexpr auto operator()(Xs&& xs, Pred&& pred) const;
};
constexpr remove_if_t remove_if{};
#endif
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_FWD_REMOVE_IF_HPP
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