From 3cac56267edfbfd26e203ad674b9b8e74e44b14e Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Mon, 19 Jan 2015 17:09:39 +0100
Subject: Implemented `Filter` in terms of `Fold` * as its name implies this
_function_ only returns elements which evaluate to _true_ when passed to a
given _function_ ** this marks the moment where _TypeAsValue_ supports
something _ConstList_ does not, i.e. primary goal is achieved *** namely
returning different types depending on the actual _values_ of a _Cons_
structure * added appropriate test case
---
src/list/operation/basic.h | 4 ++--
src/list/operation/higher/misc.h | 32 ++++++++++++++++++++++++++++----
test.cc | 8 ++++++++
3 files changed, 38 insertions(+), 6 deletions(-)
diff --git a/src/list/operation/basic.h b/src/list/operation/basic.h
index 364a542..d80b347 100644
--- a/src/list/operation/basic.h
+++ b/src/list/operation/basic.h
@@ -13,12 +13,12 @@ class Length {
typename,
typename Previous
>
- struct Count {
+ struct count {
typedef Add<Size<1>, Previous> type;
};
public:
- typedef typename Fold<Count, Size<0>, Cons>::type type;
+ typedef typename Fold<count, Size<0>, Cons>::type type;
};
diff --git a/src/list/operation/higher/misc.h b/src/list/operation/higher/misc.h
index 280c0d5..95a5f50 100644
--- a/src/list/operation/higher/misc.h
+++ b/src/list/operation/higher/misc.h
@@ -3,6 +3,7 @@
#include "fold.h"
#include "list/operation/concatenate.h"
+#include "conditional/if.h"
namespace tav {
@@ -16,12 +17,35 @@ class Map {
typename Current,
typename Previous
>
- struct FunctionWrapper {
+ struct function_wrapper {
typedef Cons<Function<Current>, Previous> type;
};
public:
- typedef typename Fold<FunctionWrapper, void, List>::type type;
+ typedef typename Fold<function_wrapper, void, List>::type type;
+
+};
+
+template <
+ template<typename> class Function,
+ typename List
+>
+class Filter {
+ private:
+ template <
+ typename Current,
+ typename Previous
+ >
+ struct function_wrapper {
+ typedef If<
+ Function<Current>::type::value,
+ Cons<Current, Previous>,
+ Previous
+ > type;
+ };
+
+ public:
+ typedef typename Fold<function_wrapper, void, List>::type type;
};
@@ -32,7 +56,7 @@ class Reverse {
typename Current,
typename Previous
>
- struct ReversedConcatenate {
+ struct reversed_concatenate {
typedef typename Concatenate<
Previous,
Cons<Current, void>
@@ -40,7 +64,7 @@ class Reverse {
};
public:
- typedef typename Fold<ReversedConcatenate, void, List>::type type;
+ typedef typename Fold<reversed_concatenate, void, List>::type type;
};
diff --git a/test.cc b/test.cc
index 655aed3..35126fb 100644
--- a/test.cc
+++ b/test.cc
@@ -14,6 +14,9 @@ class TypeAsValueTest : public ::testing::Test { };
template <typename Element>
using quadruple = tav::Multiply<tav::Int<4>, Element>;
+template <typename Element>
+using odd = tav::Boolean<(Element::value % 2 == 1)>;
+
TEST_F(TypeAsValueTest, BasicMath) {
// (+ 1 2)
EXPECT_EQ(3, ( tav::Add<tav::Int<1>, tav::Int<2>>::value ));
@@ -99,6 +102,11 @@ TEST_F(TypeAsValueTest, ListMap) {
EXPECT_TRUE(( std::is_same<tav::List<tav::Int<4>, tav::Int<8>, tav::Int<12>>::type, tav::Map<quadruple, tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>>::type>::type>::value ));
}
+TEST_F(TypeAsValueTest, ListFilter) {
+ // (filter odd (list 1 2 3))
+ EXPECT_TRUE(( std::is_same<tav::List<tav::Int<1>, tav::Int<3>>::type, tav::Filter<odd, tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>>::type>::type>::value ));
+}
+
TEST_F(TypeAsValueTest, ListReverse) {
// (reverse (list 1 2 3))
EXPECT_TRUE(( std::is_same<tav::List<tav::Int<3>, tav::Int<2>, tav::Int<1>>::type, tav::Reverse<tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>>::type>::type>::value ));
--
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