From 8b6de4c8c89d31c5d0e16548767ef21f242aadd1 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Sun, 25 Jan 2015 20:35:38 +0100
Subject: Implemented partial function application prototype * function `Apply`
 enables partial supply of the template parameters of a given _function_ **
 unsupplied parameters may be marked by _placeholders_, i.e. approach is
 similar to `std::bind` ** returns a template type taking the remaining,
 unsupplied parameters of the partially applied _function_ * this is a
 prototype in the sense, that neither full application using `Apply` or
 partial application of higher order functions is currently supported ** e.g.
 a `single_type` alias type declaration is required as the variadic template
 `template<typename...>` doesn't directly map to `template<typename>` *
 appropriate test cases document current feature set * the goal is to enable a
 concise defintion of _lambda-like_ expressions for easy specialization of
 e.g. functors provided to higher order functions

---
 src/function/apply.h | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100644 src/function/apply.h

(limited to 'src')

diff --git a/src/function/apply.h b/src/function/apply.h
new file mode 100644
index 0000000..d353169
--- /dev/null
+++ b/src/function/apply.h
@@ -0,0 +1,64 @@
+#ifndef TYPEASVALUE_SRC_FUNCTION_APPLY_H_
+#define TYPEASVALUE_SRC_FUNCTION_APPLY_H_
+
+#include <type_traits>
+
+namespace tav {
+
+namespace detail {
+
+struct placeholder_tag { };
+
+template <typename Type>
+using is_placeholder = tav::Boolean<
+	std::is_base_of<placeholder_tag, Type>::value
+>;
+
+template <int Index>
+struct placeholder : placeholder_tag { };
+
+template <
+	typename Partials,
+	typename Argument
+>
+struct resolve_placeholder {
+	typedef Argument type;
+};
+
+template <
+	typename Partials,
+	int      Index
+>
+struct resolve_placeholder<Partials, placeholder<Index>> {
+	typedef typename Nth<Size<Index>, Partials>::type type;
+};
+
+}
+
+typedef detail::placeholder<0> _0;
+typedef detail::placeholder<1> _1;
+typedef detail::placeholder<2> _2;
+typedef detail::placeholder<3> _3;
+
+template <
+	template<typename...> class Function,
+	typename...                 Arguments
+>
+struct Apply {
+	typedef typename tav::List<Arguments...>::type argument_list;
+
+	template <typename... Partials>
+	using type = Function<
+		typename detail::resolve_placeholder<
+			typename tav::List<Partials...>::type,
+			Arguments
+		>::type...
+	>;
+
+	template <typename Partials>
+	using single_type = type<Partials>;
+};
+
+}
+
+#endif  // TYPEASVALUE_SRC_FUNCTION_APPLY_H_
-- 
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