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

depends/x86_64-pc-linux-gnu/include/boost/hana/functional/curry.hpp

@@ -0,0 +1,170 @@
+/*!
+@file
+Defines `boost::hana::curry`.
+
+@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_FUNCTIONAL_CURRY_HPP
+#define BOOST_HANA_FUNCTIONAL_CURRY_HPP
+
+#include <boost/hana/config.hpp>
+#include <boost/hana/detail/decay.hpp>
+#include <boost/hana/functional/apply.hpp>
+#include <boost/hana/functional/partial.hpp>
+
+#include <cstddef>
+#include <type_traits>
+#include <utility>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! @ingroup group-functional
+    //! Curry a function up to the given number of arguments.
+    //!
+    //! [Currying][Wikipedia.currying] is a technique in which we consider a
+    //! function taking multiple arguments (or, equivalently, a tuple of
+    //! arguments), and turn it into a function which takes a single argument
+    //! and returns a function to handle the remaining arguments. To help
+    //! visualize, let's denote the type of a function `f` which takes
+    //! arguments of types `X1, ..., Xn` and returns a `R` as
+    //! @code
+    //!     (X1, ..., Xn) -> R
+    //! @endcode
+    //!
+    //! Then, currying is the process of taking `f` and turning it into an
+    //! equivalent function (call it `g`) of type
+    //! @code
+    //!     X1 -> (X2 -> (... -> (Xn -> R)))
+    //! @endcode
+    //!
+    //! This gives us the following equivalence, where `x1`, ..., `xn` are
+    //! objects of type `X1`, ..., `Xn` respectively:
+    //! @code
+    //!     f(x1, ..., xn) == g(x1)...(xn)
+    //! @endcode
+    //!
+    //! Currying can be useful in several situations, especially when working
+    //! with higher-order functions.
+    //!
+    //! This `curry` utility is an implementation of currying in C++.
+    //! Specifically, `curry<n>(f)` is a function such that
+    //! @code
+    //!     curry<n>(f)(x1)...(xn) == f(x1, ..., xn)
+    //! @endcode
+    //!
+    //! Note that the `n` has to be specified explicitly because the existence
+    //! of functions with variadic arguments in C++ make it impossible to know
+    //! when currying should stop.
+    //!
+    //! Unlike usual currying, this implementation also allows a curried
+    //! function to be called with several arguments at a time. Hence, the
+    //! following always holds
+    //! @code
+    //!     curry<n>(f)(x1, ..., xk) == curry<n - k>(f)(x1)...(xk)
+    //! @endcode
+    //!
+    //! Of course, this requires `k` to be less than or equal to `n`; failure
+    //! to satisfy this will trigger a static assertion. This syntax is
+    //! supported because it makes curried functions usable where normal
+    //! functions are expected.
+    //!
+    //! Another "extension" is that `curry<0>(f)` is supported: `curry<0>(f)`
+    //! is a nullary function; whereas the classical definition for currying
+    //! seems to leave this case undefined, as nullary functions don't make
+    //! much sense in purely functional languages.
+    //!
+    //!
+    //! Example
+    //! -------
+    //! @include example/functional/curry.cpp
+    //!
+    //!
+    //! [Wikipedia.currying]: http://en.wikipedia.org/wiki/Currying
+#ifdef BOOST_HANA_DOXYGEN_INVOKED
+    template <std::size_t n>
+    constexpr auto curry = [](auto&& f) {
+        return [perfect-capture](auto&& x1) {
+            return [perfect-capture](auto&& x2) {
+                ...
+                    return [perfect-capture](auto&& xn) -> decltype(auto) {
+                        return forwarded(f)(
+                            forwarded(x1), forwarded(x2), ..., forwarded(xn)
+                        );
+                    };
+            };
+        };
+    };
+#else
+    template <std::size_t n, typename F>
+    struct curry_t;
+
+    template <std::size_t n>
+    struct make_curry_t {
+        template <typename F>
+        constexpr curry_t<n, typename detail::decay<F>::type>
+        operator()(F&& f) const { return {static_cast<F&&>(f)}; }
+    };
+
+    template <std::size_t n>
+    constexpr make_curry_t<n> curry{};
+
+    namespace curry_detail {
+        template <std::size_t n>
+        constexpr make_curry_t<n> curry_or_call{};
+
+        template <>
+        constexpr auto curry_or_call<0> = apply;
+    }
+
+    template <std::size_t n, typename F>
+    struct curry_t {
+        F f;
+
+        template <typename ...X>
+        constexpr decltype(auto) operator()(X&& ...x) const& {
+            static_assert(sizeof...(x) <= n,
+            "too many arguments provided to boost::hana::curry");
+            return curry_detail::curry_or_call<n - sizeof...(x)>(
+                partial(f, static_cast<X&&>(x)...)
+            );
+        }
+
+        template <typename ...X>
+        constexpr decltype(auto) operator()(X&& ...x) & {
+            static_assert(sizeof...(x) <= n,
+            "too many arguments provided to boost::hana::curry");
+            return curry_detail::curry_or_call<n - sizeof...(x)>(
+                partial(f, static_cast<X&&>(x)...)
+            );
+        }
+
+        template <typename ...X>
+        constexpr decltype(auto) operator()(X&& ...x) && {
+            static_assert(sizeof...(x) <= n,
+            "too many arguments provided to boost::hana::curry");
+            return curry_detail::curry_or_call<n - sizeof...(x)>(
+                partial(std::move(f), static_cast<X&&>(x)...)
+            );
+        }
+    };
+
+    template <typename F>
+    struct curry_t<0, F> {
+        F f;
+
+        constexpr decltype(auto) operator()() const&
+        { return f(); }
+
+        constexpr decltype(auto) operator()() &
+        { return f(); }
+
+        constexpr decltype(auto) operator()() &&
+        { return std::move(f)(); }
+    };
+#endif
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_FUNCTIONAL_CURRY_HPP