stabilize build system: depends, installer, boost/bdb fixes, cross targets groundwork

depends/x86_64-pc-linux-gnu/include/boost/hana/fwd/while.hpp

@@ -0,0 +1,71 @@
+/*!
+@file
+Forward declares `boost::hana::while_`.
+
+@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_WHILE_HPP
+#define BOOST_HANA_FWD_WHILE_HPP
+
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/when.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! Apply a function to an initial state while some predicate is satisfied.
+    //! @ingroup group-Logical
+    //!
+    //! This method is a natural extension of the `while` language construct
+    //! to manipulate a state whose type may change from one iteration to
+    //! another. However, note that having a state whose type changes from
+    //! one iteration to the other is only possible as long as the predicate
+    //! returns a `Logical` whose truth value is known at compile-time.
+    //!
+    //! Specifically, `while_(pred, state, f)` is equivalent to
+    //! @code
+    //!     f(...f(f(state)))
+    //! @endcode
+    //! where `f` is iterated as long as `pred(f(...))` is a true-valued
+    //! `Logical`.
+    //!
+    //!
+    //! @param pred
+    //! A predicate called on the state or on the result of applying `f` a
+    //! certain number of times to the state, and returning whether `f`
+    //! should be applied one more time.
+    //!
+    //! @param state
+    //! The initial state on which `f` is applied.
+    //!
+    //! @param f
+    //! A function that is iterated on the initial state. Note that the
+    //! return type of `f` may change from one iteration to the other,
+    //! but only while `pred` returns a compile-time `Logical`. In other
+    //! words, `decltype(f(stateN))` may differ from `decltype(f(stateN+1))`,
+    //! but only if `pred(f(stateN))` returns a compile-time `Logical`.
+    //!
+    //!
+    //! Example
+    //! -------
+    //! @include example/while.cpp
+#ifdef BOOST_HANA_DOXYGEN_INVOKED
+    constexpr auto while_ = [](auto&& pred, auto&& state, auto&& f) -> decltype(auto) {
+        return tag-dispatched;
+    };
+#else
+    template <typename L, typename = void>
+    struct while_impl : while_impl<L, when<true>> { };
+
+    struct while_t {
+        template <typename Pred, typename State, typename F>
+        constexpr decltype(auto) operator()(Pred&& pred, State&& state, F&& f) const;
+    };
+
+    constexpr while_t while_{};
+#endif
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_FWD_WHILE_HPP