From 246cb31c1e20cdcc21a6a607de4b0095c71315d6 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Thu, 12 Feb 2015 14:32:33 +0100
Subject: Implemented `Cond` conditional * returns the `CDR` of the first true
 `CAR` in a given list of pairs * reimplemented `Apply` base class selection
 in terms of `Cond`

---
 src/conditional/cond.h      | 29 +++++++++++++++++++++++++++++
 src/function/apply.h        | 26 ++++++++++++++++++--------
 src/function/detail/apply.h |  8 ++++++++
 src/type.h                  |  3 +++
 4 files changed, 58 insertions(+), 8 deletions(-)
 create mode 100644 src/conditional/cond.h

(limited to 'src')

diff --git a/src/conditional/cond.h b/src/conditional/cond.h
new file mode 100644
index 0000000..0c2b1a8
--- /dev/null
+++ b/src/conditional/cond.h
@@ -0,0 +1,29 @@
+#ifndef TYPEASVALUE_SRC_CONDITIONAL_COND_H_
+#define TYPEASVALUE_SRC_CONDITIONAL_COND_H_
+
+#include <type_traits>
+
+#include "list/list.h"
+#include "list/operation/higher/find.h"
+
+namespace tav {
+
+template <typename... Branches>
+class Cond {
+	private:
+		template <typename Pair>
+		using predicate = IsTrue<typename Car<Pair>::type::type>;
+
+	public:
+		typedef typename Cdr<
+			typename Find<
+				predicate,
+				typename List<Branches...>::type
+			>::type
+		>::type type;
+
+};
+
+}
+
+#endif  // TYPEASVALUE_SRC_CONDITIONAL_COND_H_
diff --git a/src/function/apply.h b/src/function/apply.h
index 21364a8..5a2105c 100644
--- a/src/function/apply.h
+++ b/src/function/apply.h
@@ -1,7 +1,8 @@
 #ifndef TYPEASVALUE_SRC_FUNCTION_APPLY_H_
 #define TYPEASVALUE_SRC_FUNCTION_APPLY_H_
 
-#include "conditional/if.h"
+#include "operation/math.h"
+#include "conditional/cond.h"
 
 #include "detail/apply.h"
 
@@ -16,14 +17,23 @@ template <
 	template<typename...> class Function,
 	typename...                 Arguments
 >
-struct Apply : If<
-	(detail::count_placeholders<Arguments...>::type::value > 2),
-	detail::apply_variadic<Function, Arguments...>,
-	typename If<
-		detail::count_placeholders<Arguments...>::type::value == 2,
-		detail::apply_pair<Function, Arguments...>,
+struct Apply : Cond<
+	Pair<
+		GreaterThan<typename detail::count_placeholders<Arguments...>::type,  Size<2>>,
+		detail::apply_variadic<Function, Arguments...>
+	>,
+	Pair<
+		IsEqualValue<typename detail::count_placeholders<Arguments...>::type, Size<2>>,
+		detail::apply_pair<Function, Arguments...>
+	>,
+	Pair<
+		IsEqualValue<typename detail::count_placeholders<Arguments...>::type, Size<1>>,
 		detail::apply_single<Function, Arguments...>
-	>::type
+	>,
+	Pair<
+		Boolean<true>,
+		detail::apply_none<Function, Arguments...>
+	>
 >::type { };
 
 }
diff --git a/src/function/detail/apply.h b/src/function/detail/apply.h
index bf60be1..d9f058a 100644
--- a/src/function/detail/apply.h
+++ b/src/function/detail/apply.h
@@ -42,6 +42,14 @@ using count_placeholders = Count<
 	typename List<Arguments...>::type
 >;
 
+template <
+	template<typename...> class Function,
+	typename...                 Arguments
+>
+struct apply_none {
+	using type = Function<Arguments...>;
+};
+
 template <
 	template<typename...> class Function,
 	typename...                 Arguments
diff --git a/src/type.h b/src/type.h
index c175c36..15ba2f8 100644
--- a/src/type.h
+++ b/src/type.h
@@ -32,6 +32,9 @@ template <
 >
 using IsEqualValue = Boolean<X::value == Y::value>;
 
+template <typename X>
+using IsTrue = IsEqualValue<X, Boolean<true>>;
+
 }
 
 #endif  // TYPEASVALUE_SRC_TYPE_H_
-- 
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