From 385c51950644121d7b6e04718374b1af63209ac7 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Sat, 17 Jan 2015 17:28:02 +0100
Subject: Implemented `Length` function * as its name implies this function
 returns the length of a given _Cons_ structure * result type is
 `Size<Length>` which wraps `std::size_t` to match the `sizeof` operator

---
 src/conditional/if.h |  8 ++++----
 src/list/list.h      | 10 ++++++++++
 src/type.h           |  3 +++
 test.cc              | 14 ++++++++++++--
 4 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/src/conditional/if.h b/src/conditional/if.h
index 29aa6f0..b9568f6 100644
--- a/src/conditional/if.h
+++ b/src/conditional/if.h
@@ -7,13 +7,13 @@ namespace tav {
 
 template <
 	bool     Condition,
-	typename IfBranch,
-	typename ElseBranch
+	typename TrueBranch,
+	typename FalseBranch
 >
 using If = typename std::conditional<
 	Condition,
-	IfBranch,
-	ElseBranch
+	TrueBranch,
+	FalseBranch
 >::type;
 
 }
diff --git a/src/list/list.h b/src/list/list.h
index edd46e8..f21d0fc 100644
--- a/src/list/list.h
+++ b/src/list/list.h
@@ -27,6 +27,16 @@ using Head = Car<Cons>;
 template <typename Cons>
 using Tail = Cdr<Cons>;
 
+template <typename Cons>
+struct Length {
+	typedef Add<Size<1>, typename Length<Cdr<Cons>>::type> type;
+};
+
+template <>
+struct Length<void> {
+	typedef Size<0> type;
+};
+
 template <
 	typename Primary,
 	typename Secondary
diff --git a/src/type.h b/src/type.h
index 304bff4..74e0650 100644
--- a/src/type.h
+++ b/src/type.h
@@ -8,6 +8,9 @@ namespace tav {
 template <int Value>
 using Int = typename std::integral_constant<int, Value>::type;
 
+template <std::size_t Value>
+using Size = typename std::integral_constant<std::size_t, Value>::type;
+
 template <bool Value>
 using Boolean = typename std::integral_constant<bool, Value>::type;
 
diff --git a/test.cc b/test.cc
index 390804b..6ce3691 100644
--- a/test.cc
+++ b/test.cc
@@ -21,9 +21,9 @@ TEST_F(TypeAsValueTest, BasicMath) {
 
 TEST_F(TypeAsValueTest, Conditional) {
 	// (if #t 1 2)
-	EXPECT_EQ(1, ( tav::If<true,  tav::Int<1>, tav::Int<2>>::value ));
+	EXPECT_EQ(1, ( tav::If<true,  tav::Int<1>, tav::Int<2>>::type::value ));
 	// (if #f 1 2)
-	EXPECT_EQ(2, ( tav::If<false, tav::Int<1>, tav::Int<2>>::value ));
+	EXPECT_EQ(2, ( tav::If<false, tav::Int<1>, tav::Int<2>>::type::value ));
 }
 
 TEST_F(TypeAsValueTest, Cons) {
@@ -38,6 +38,11 @@ TEST_F(TypeAsValueTest, Cons) {
 }
 
 TEST_F(TypeAsValueTest, List) {
+	// (length (list 1))
+	EXPECT_EQ(1, ( tav::Length<tav::List<tav::Int<1>>::type>::type::value ));
+	// (length (list 1 2))
+	EXPECT_EQ(2, ( tav::Length<tav::List<tav::Int<1>, tav::Int<2>>::type>::type::value ));
+
 	// (head (list 1))
 	EXPECT_EQ(1, ( tav::Head<tav::List<tav::Int<1>>::type>::value ));
 	// (head (list 1 2))
@@ -49,6 +54,11 @@ TEST_F(TypeAsValueTest, List) {
 }
 
 TEST_F(TypeAsValueTest, ListConcatenate) {
+	// (length (concatenate (list 1) (list 2)))
+	EXPECT_EQ(2, ( tav::Length<tav::Concatenate<tav::List<tav::Int<1>>::type, tav::List<tav::Int<2>>::type>::type>::type::value ));
+	// (length (concatenate (list 1 2) (list 3 4)))
+	EXPECT_EQ(4, ( tav::Length<tav::Concatenate<tav::List<tav::Int<1>, tav::Int<2>>::type, tav::List<tav::Int<3>, tav::Int<4>>::type>::type>::type::value ));
+
 	// (head (concatenate (list 1) (list 2)))
 	EXPECT_EQ(1, ( tav::Head<tav::Concatenate<tav::List<tav::Int<1>>::type, tav::List<tav::Int<2>>::type>::type>::value ));
 	// (head (tail (concatenate (list 1) (list 2))))
-- 
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