From d2f725f6fe602cbd2fc729465d412ea25b0a7673 Mon Sep 17 00:00:00 2001
From: Louis Dionne <ldionne.2@gmail.com>
Date: Sun, 25 May 2014 11:06:18 -0400
Subject: [PATCH] Add Typelist; an optimized List for types.

---
 include/boost/hana.hpp          |  1 +
 include/boost/hana/typelist.hpp | 92 +++++++++++++++++++++++++++++++++
 test/CMakeLists.txt             |  4 ++
 test/typelist/comparable.cpp    | 25 +++++++++
 test/typelist/functor.cpp       | 47 +++++++++++++++++
 test/typelist/iterable.cpp      | 29 +++++++++++
 6 files changed, 198 insertions(+)
 create mode 100644 include/boost/hana/typelist.hpp
 create mode 100644 test/typelist/comparable.cpp
 create mode 100644 test/typelist/functor.cpp
 create mode 100644 test/typelist/iterable.cpp

diff --git a/include/boost/hana.hpp b/include/boost/hana.hpp
index 4135fe0bd..37631e05c 100644
--- a/include/boost/hana.hpp
+++ b/include/boost/hana.hpp
@@ -45,5 +45,6 @@
 #include <boost/hana/range.hpp>
 #include <boost/hana/trait.hpp>
 #include <boost/hana/type.hpp>
+#include <boost/hana/typelist.hpp>
 
 #endif // !BOOST_HANA_HPP
diff --git a/include/boost/hana/typelist.hpp b/include/boost/hana/typelist.hpp
new file mode 100644
index 000000000..6b82c3c20
--- /dev/null
+++ b/include/boost/hana/typelist.hpp
@@ -0,0 +1,92 @@
+/*!
+ * @file
+ * Defines `boost::hana::Typelist`.
+ *
+ *
+ * @copyright Louis Dionne 2014
+ * Distributed under the Boost Software License, Version 1.0.
+ *         (See accompanying file LICENSE.md or copy at
+ *             http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#ifndef BOOST_HANA_TYPELIST_HPP
+#define BOOST_HANA_TYPELIST_HPP
+
+#include <boost/hana/comparable.hpp>
+#include <boost/hana/detail/comparable_from_iterable.hpp>
+#include <boost/hana/detail/foldable_from_iterable.hpp>
+#include <boost/hana/detail/left_folds/variadic.hpp>
+#include <boost/hana/detail/left_folds/variadic_meta.hpp>
+#include <boost/hana/foldable.hpp>
+#include <boost/hana/functor.hpp>
+#include <boost/hana/integral.hpp>
+#include <boost/hana/iterable.hpp>
+#include <boost/hana/list.hpp>
+#include <boost/hana/type.hpp>
+
+
+namespace boost { namespace hana {
+    //! @ingroup datatypes
+    template <typename ...Xs>
+    struct Typelist { };
+
+    template <typename ...Xs>
+    constexpr auto typelist = Typelist<Xs...>{};
+
+    template <typename X, typename ...Xs>
+    struct Iterable<Typelist<X, Xs...>> {
+        static constexpr auto head_impl(Typelist<X, Xs...>)
+        { return type<X>; }
+
+        static constexpr auto tail_impl(Typelist<X, Xs...>)
+        { return typelist<Xs...>; }
+
+        static constexpr auto is_empty_impl(Typelist<X, Xs...>)
+        { return false_; }
+    };
+
+    template <>
+    struct Iterable<Typelist<>> {
+        static constexpr auto is_empty_impl(Typelist<>)
+        { return true_; }
+    };
+
+    template <typename ...Xs>
+    struct Functor<Typelist<Xs...>> : defaults<Functor> {
+        template <typename F>
+        static constexpr auto fmap_impl(F f, Typelist<Xs...>)
+        { return list(f(type<Xs>)...); }
+
+        template <template <typename ...> class F>
+        static constexpr auto fmap_impl(type_detail::Lift<F>, Typelist<Xs...>)
+        { return typelist<F<Xs>...>; }
+    };
+
+    template <typename ...Xs>
+    struct Foldable<Typelist<Xs...>> : detail::foldable_from_iterable {
+        template <typename F, typename State>
+        static constexpr auto foldl_impl(F f, State s, Typelist<Xs...>) {
+            return detail::left_folds::variadic(f, s, type<Xs>...);
+        }
+
+        template <template <typename ...> class F, typename State>
+        static constexpr auto foldl_impl(type_detail::Lift<F>, Type<State>, Typelist<Xs...>) {
+            return type<detail::left_folds::variadic_meta<F, State, Xs...>>;
+        }
+    };
+
+    template <typename ...Xs, typename ...Ys>
+    struct Comparable<Typelist<Xs...>, Typelist<Ys...>>
+        : detail::comparable_from_iterable
+    { };
+
+    template <typename ...Xs, typename ...Ys>
+    constexpr auto operator==(Typelist<Xs...> xs, Typelist<Ys...> ys)
+    {  return equal(xs, ys); }
+
+    template <typename ...Xs, typename ...Ys>
+    constexpr auto operator!=(Typelist<Xs...> xs, Typelist<Ys...> ys)
+    {  return not_equal(xs, ys); }
+}} // end namespace boost::hana
+
+#endif // !BOOST_HANA_TYPELIST_HPP
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 204a6bb08..ba717f452 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -71,6 +71,10 @@ boost_hana_add_test(type.comparable)
 boost_hana_add_test(type.lift)
 boost_hana_add_test(type.traits)
 
+boost_hana_add_test(typelist.comparable)
+boost_hana_add_test(typelist.functor)
+boost_hana_add_test(typelist.iterable)
+
 
 boost_hana_add_test(hana)
 boost_hana_add_test(misc.adl)
diff --git a/test/typelist/comparable.cpp b/test/typelist/comparable.cpp
new file mode 100644
index 000000000..6fee2addb
--- /dev/null
+++ b/test/typelist/comparable.cpp
@@ -0,0 +1,25 @@
+/*
+ * Copyright Louis Dionne 2014
+ * Distributed under the Boost Software License, Version 1.0.
+ *         (See accompanying file LICENSE.md or copy at
+ *             http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include <boost/hana/typelist.hpp>
+
+#include <boost/hana/detail/static_assert.hpp>
+using namespace boost::hana;
+
+
+struct x0; struct x1; struct x2;
+
+int main() {
+    BOOST_HANA_STATIC_ASSERT(typelist<> == typelist<>);
+    BOOST_HANA_STATIC_ASSERT(typelist<x0> != typelist<>);
+    BOOST_HANA_STATIC_ASSERT(typelist<> != typelist<x0>);
+    BOOST_HANA_STATIC_ASSERT(typelist<x0> == typelist<x0>);
+    BOOST_HANA_STATIC_ASSERT(typelist<x0, x1> != typelist<x0>);
+    BOOST_HANA_STATIC_ASSERT(typelist<x0> != typelist<x0, x1>);
+    BOOST_HANA_STATIC_ASSERT(typelist<x0, x1> == typelist<x0, x1>);
+    BOOST_HANA_STATIC_ASSERT(typelist<x0, x1, x2> == typelist<x0, x1, x2>);
+}
diff --git a/test/typelist/functor.cpp b/test/typelist/functor.cpp
new file mode 100644
index 000000000..36c6453e7
--- /dev/null
+++ b/test/typelist/functor.cpp
@@ -0,0 +1,47 @@
+/*
+ * Copyright Louis Dionne 2014
+ * Distributed under the Boost Software License, Version 1.0.
+ *         (See accompanying file LICENSE.md or copy at
+ *             http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include <boost/hana/typelist.hpp>
+
+#include <boost/hana/detail/static_assert.hpp>
+#include <boost/hana/list.hpp>
+#include <boost/hana/type.hpp>
+using namespace boost::hana;
+
+
+struct x0; struct x1; struct x2;
+
+
+constexpr struct {
+    constexpr auto operator()(Type<x0>) const { return 0; }
+    constexpr auto operator()(Type<x1>) const { return 1; }
+    constexpr auto operator()(Type<x2>) const { return 2; }
+} fv{};
+
+void test_values() {
+    BOOST_HANA_STATIC_ASSERT(fmap(fv, typelist<>) == list());
+    BOOST_HANA_STATIC_ASSERT(fmap(fv, typelist<x0>) == list(0));
+    BOOST_HANA_STATIC_ASSERT(fmap(fv, typelist<x0, x1>) == list(0, 1));
+    BOOST_HANA_STATIC_ASSERT(fmap(fv, typelist<x0, x1, x2>) == list(0, 1, 2));
+}
+
+
+template <typename ...> struct _ft { };
+constexpr auto ft = lift<_ft>;
+
+void test_types() {
+    BOOST_HANA_STATIC_ASSERT(fmap(ft, typelist<>) == typelist<>);
+    BOOST_HANA_STATIC_ASSERT(fmap(ft, typelist<x0>) == typelist<_ft<x0>>);
+    BOOST_HANA_STATIC_ASSERT(fmap(ft, typelist<x0, x1>) == typelist<_ft<x0>, _ft<x1>>);
+    BOOST_HANA_STATIC_ASSERT(fmap(ft, typelist<x0, x1, x2>) == typelist<_ft<x0>, _ft<x1>, _ft<x2>>);
+}
+
+
+int main() {
+    test_values();
+    test_types();
+}
diff --git a/test/typelist/iterable.cpp b/test/typelist/iterable.cpp
new file mode 100644
index 000000000..6f973555d
--- /dev/null
+++ b/test/typelist/iterable.cpp
@@ -0,0 +1,29 @@
+/*
+ * Copyright Louis Dionne 2014
+ * Distributed under the Boost Software License, Version 1.0.
+ *         (See accompanying file LICENSE.md or copy at
+ *             http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#include <boost/hana/typelist.hpp>
+
+#include <boost/hana/detail/static_assert.hpp>
+#include <boost/hana/type.hpp>
+using namespace boost::hana;
+
+
+struct x0; struct x1; struct x2;
+
+int main() {
+    BOOST_HANA_STATIC_ASSERT(is_empty(typelist<>));
+    BOOST_HANA_STATIC_ASSERT(!is_empty(typelist<x0>));
+    BOOST_HANA_STATIC_ASSERT(!is_empty(typelist<x0, x1>));
+
+    BOOST_HANA_STATIC_ASSERT(head(typelist<x0>) == type<x0>);
+    BOOST_HANA_STATIC_ASSERT(head(typelist<x0, x1>) == type<x0>);
+    BOOST_HANA_STATIC_ASSERT(head(typelist<x0, x1, x2>) == type<x0>);
+
+    BOOST_HANA_STATIC_ASSERT(tail(typelist<x0>) == typelist<>);
+    BOOST_HANA_STATIC_ASSERT(tail(typelist<x0, x1>) == typelist<x1>);
+    BOOST_HANA_STATIC_ASSERT(tail(typelist<x0, x1, x2>) == typelist<x1, x2>);
+}