Merge pull request #6 from njoy/feature/TransformIterator

Feature/transform iterator

cmake/unit_testing.cmake

@@ -29,3 +29,6 @@ endfunction()
 add_subdirectory( src/tools/Log/test )
 
 add_subdirectory( src/tools/ranges/IteratorView/test )
+add_subdirectory( src/tools/ranges/TransformIterator/test )
+add_subdirectory( src/tools/ranges/make_view/test )
+add_subdirectory( src/tools/ranges/make_transform_view/test )

src/tools/ranges.hpp

@@ -1 +1,5 @@
 #include "tools/ranges/IteratorView.hpp"
+#include "tools/ranges/TransformIterator.hpp"
+
+#include "tools/ranges/make_view.hpp"
+#include "tools/ranges/make_transform_view.hpp"

src/tools/ranges/IteratorView.hpp

@@ -49,7 +49,7 @@ class IteratorView {
   constexpr IteratorView() : IteratorView( Iterator{}, Iterator{} ) {}
 
   /**
-   *  @brief IteratorView constructor
+   *  @brief Constructor
    *
    *  @param[in] begin    the iterator to the beginning of the view
    *  @param[in] end      the iterator to the end of the view
@@ -149,43 +149,6 @@ class IteratorView {
   }
 };
 
-/**
- *  @brief Make an IteratorView based on two iterators
- *
- *  @param[in] begin    the iterator to the beginning of the view
- *  @param[in] end      the iterator to the end of the view
- */
-template < typename Iterator >
-constexpr auto make_view( Iterator&& begin, Iterator&& end ) {
-
-  return IteratorView< Iterator >{ std::forward< Iterator >( begin ),
-                                   std::forward< Iterator >( end ) };
-}
-
-/**
- *  @brief Make an IteratorView based on a container
- *
- *  @param[in] container    the container
- */
-template < typename Container >
-constexpr auto make_view( Container& container ) {
-
-  return IteratorView< typename Container::iterator >{ container.begin(),
-                                                       container.end() };
-}
-
-/**
- *  @brief Make an IteratorView based on a container
- *
- *  @param[in] container    the container
- */
-template < typename Container >
-constexpr auto make_view( const Container& container ) {
-
-  return IteratorView< typename Container::const_iterator >{ container.cbegin(),
-                                                             container.cend() };
-}
-
 /**
  *  @brief Verify if the IteratorView is equal to another container
  *

src/tools/ranges/IteratorView/test/IteratorView.test.cpp

@@ -49,41 +49,6 @@ SCENARIO( "IteratorView" ) {
         CHECK_THROWS( chunk.at( 10 ) );
       } // THEN
     } // WHEN
-
-    WHEN( "when make functions are used" ) {
-
-      auto chunk = make_view( values );
-
-      THEN( "an IteratorView can be constructed and members can be tested" ) {
-
-        CHECK( 5 == chunk.size() );
-        CHECK( false == chunk.empty() );
-
-        CHECK( -2 == chunk[0] );
-        CHECK( -1 == chunk[1] );
-        CHECK(  0 == chunk[2] );
-        CHECK(  1 == chunk[3] );
-        CHECK(  2 == chunk[4] );
-
-        CHECK( -2 == chunk.at( 0 ) );
-        CHECK( -1 == chunk.at( 1 ) );
-        CHECK(  0 == chunk.at( 2 ) );
-        CHECK(  1 == chunk.at( 3 ) );
-        CHECK(  2 == chunk.at( 4 ) );
-
-        CHECK( -2 == chunk.front() );
-        CHECK(  2 == chunk.back() );
-      } // THEN
-
-      THEN( "an exception is thrown when using an index that is too large or "
-            "too small" ) {
-
-        CHECK_NOTHROW( chunk.at( 0 ) );
-        CHECK_NOTHROW( chunk.at( 4 ) );
-        CHECK_THROWS( chunk.at( 5 ) );
-        CHECK_THROWS( chunk.at( 10 ) );
-      } // THEN
-    } // WHEN
   } // GIVEN
 
   GIVEN( "containers and views with values" ) {
@@ -94,8 +59,8 @@ SCENARIO( "IteratorView" ) {
     std::vector< double > copy1 = container1;
     std::vector< double > copy2 = container2;
 
-    auto view1 = make_view( copy1 );
-    auto view2 = make_view( copy2 );
+    IteratorView< std::vector< double >::iterator > view1( copy1.begin(), copy1.end() );
+    IteratorView< std::vector< double >::iterator > view2( copy2.begin(), copy2.end() );
 
     WHEN( "when make comparison functions are used" ) {
 

src/tools/ranges/TransformIterator.hpp

@@ -0,0 +1,157 @@
+#ifndef NJOY_UTILITY_TRANSFORMITERATOR
+#define NJOY_UTILITY_TRANSFORMITERATOR
+
+// system includes
+#include <iterator>
+
+// other includes
+
+namespace njoy {
+namespace tools {
+namespace ranges {
+
+/**
+ *
+ *  @brief An iterator class that applies a transformation when dereferencing
+ *         the iterator
+ */
+template < typename Iterator, typename Transformation >
+class TransformIterator {
+
+  /* fields */
+  Iterator iter_;
+  Transformation transform_;
+
+public:
+
+  using iterator_category = typename Iterator::iterator_category;
+  using difference_type = typename Iterator::difference_type;
+  using value_type = decltype( std::declval< Transformation >()( std::declval< typename Iterator::value_type >() ) );
+  using pointer = value_type*;
+  using reference = value_type;
+
+  /* constructor */
+
+  constexpr TransformIterator() = delete;
+
+  /**
+   *  @brief Constructor
+   *
+   *  @param[in] iter              the iterator
+   *  @param[in] transformation    the transformation to be applied
+   */
+  constexpr TransformIterator( Iterator iter, Transformation transformation ) :
+    iter_( std::move( iter ) ), transform_( std::move( transformation ) ) {}
+
+  /* methods */
+
+  constexpr reference operator*() const {
+
+    return this->transform_( *this->iter_ );
+  }
+
+  constexpr reference operator[]( difference_type i ) const {
+
+    return this->transform_( this->iter_[i] );
+  }
+
+  constexpr TransformIterator& operator+=( difference_type i ) {
+
+    this->iter_ += i;
+    return *this;
+  }
+
+  constexpr TransformIterator& operator-=( difference_type i ) {
+
+    this->iter_ -= i;
+    return *this;
+  }
+
+  constexpr TransformIterator& operator++( void ) {
+
+    ++this->iter_;
+    return *this;
+  }
+
+  constexpr TransformIterator operator++( int ) {
+
+    return TransformIterator( this->iter_++, transform_ );
+  }
+
+  constexpr TransformIterator& operator--( void ) {
+
+    --this->iter_;
+    return *this;
+  }
+
+  constexpr TransformIterator operator--( int ) {
+
+    return TransformIterator( this->iter_--, this->transform_ );
+  }
+
+  friend constexpr TransformIterator operator+( difference_type i,
+                                                TransformIterator iter ) {
+
+    return TransformIterator( iter.iter_ + i, iter.transform_ );
+  }
+
+  friend constexpr TransformIterator operator+( TransformIterator iter,
+                                                difference_type i ) {
+
+    return TransformIterator( iter.iter_ + i, iter.transform_ );
+  }
+
+  friend constexpr TransformIterator operator-( TransformIterator iter,
+                                                difference_type i ) {
+
+    return TransformIterator( iter.iter_ - i, iter.transform_ );
+  }
+
+  friend constexpr difference_type operator-( const TransformIterator& left,
+                                              const TransformIterator& right ) {
+
+    return left.iter_ - right.iter_;
+  }
+
+  friend constexpr bool operator==( const TransformIterator& left,
+                                    const TransformIterator& right ) {
+
+    return left.iter_ == right.iter_;
+  };
+
+  friend constexpr bool operator!=( const TransformIterator& left,
+                                    const TransformIterator& right ) {
+
+    return !( left == right );
+  };
+
+  friend constexpr bool operator<( const TransformIterator& left,
+                                   const TransformIterator& right) {
+
+      return left.iter_ < right.iter_;
+  }
+
+  friend constexpr bool operator>( const TransformIterator& left,
+                                   const TransformIterator& right ) {
+
+      return right < left;
+  }
+
+  friend constexpr bool operator<=( const TransformIterator& left,
+                                    const TransformIterator& right ) {
+
+      return !( right < left );
+  }
+
+  friend constexpr bool operator>=( const TransformIterator& left,
+                                    const TransformIterator& right ) {
+
+      return !( left < right );
+  }
+};
+
+} // ranges namespace
+} // tools namespace
+} // njoy namespace
+
+#endif

src/tools/ranges/TransformIterator/test/CMakeLists.txt

@@ -0,0 +1 @@
+add_cpp_test( ranges.TransformIterator TransformIterator.test.cpp )

src/tools/ranges/TransformIterator/test/TransformIterator.test.cpp

@@ -0,0 +1,85 @@
+// include Catch2
+#include <catch2/catch_test_macros.hpp>
+
+// what we are testing
+#include "tools/ranges/TransformIterator.hpp"
+
+// other includes
+
+// convenience typedefs
+using namespace njoy::tools::ranges;
+
+SCENARIO( "TransformIterator" ) {
+
+  GIVEN( "a container with values and a transformation operation" ) {
+
+    std::vector< int > values = { -2, -1, 0, 1, 2 };
+    auto transform = [] ( auto&& value ) { return 2 * value; };
+
+    WHEN( "when iterators are used" ) {
+
+      TransformIterator iter( values.begin(), transform );
+      TransformIterator begin( values.begin(), transform );
+      TransformIterator end( values.end(), transform );
+
+      THEN( "TransformIterator behaves as an iterator" ) {
+
+        CHECK( *iter == -4 );
+
+        CHECK( iter[0] == -4 );
+        CHECK( iter[1] == -2 );
+        CHECK( iter[2] ==  0 );
+        CHECK( iter[3] ==  2 );
+        CHECK( iter[4] ==  4 );
+
+        CHECK( *( begin + 0 ) == -4 );
+        CHECK( *( begin + 1 ) == -2 );
+        CHECK( *( begin + 2 ) ==  0 );
+        CHECK( *( begin + 3 ) ==  2 );
+        CHECK( *( begin + 4 ) ==  4 );
+
+        CHECK( *( 0 + begin ) == -4 );
+        CHECK( *( 1 + begin ) == -2 );
+        CHECK( *( 2 + begin ) ==  0 );
+        CHECK( *( 3 + begin ) ==  2 );
+        CHECK( *( 4 + begin ) ==  4 );
+
+        CHECK( *( end - 1 ) ==  4 );
+        CHECK( *( end - 2 ) ==  2 );
+        CHECK( *( end - 3 ) ==  0 );
+        CHECK( *( end - 4 ) == -2 );
+        CHECK( *( end - 5 ) == -4 );
+
+        CHECK( end - begin ==  5 );
+
+        iter += 3;
+        CHECK( *iter ==  2 );
+        iter -= 3;
+        CHECK( *iter == -4 );
+
+        ++iter;
+        CHECK( *iter == -2 );
+        --iter;
+        CHECK( *iter == -4 );
+
+        CHECK( *( iter++ ) == -4 );
+        CHECK( *iter == -2 );
+        CHECK( *( iter-- ) == -2 );
+        CHECK( *iter == -4 );
+
+        CHECK( true  == ( iter == begin ) );
+        CHECK( false == ( iter == end ) );
+        CHECK( true  == ( iter != end ) );
+        CHECK( false == ( iter != begin ) );
+        CHECK( true  == ( iter < end ) );
+        CHECK( false == ( iter < begin ) );
+        CHECK( true  == ( iter <= begin ) );
+        CHECK( false == ( end <= iter ) );
+        CHECK( true  == ( end > iter ) );
+        CHECK( false == ( iter > begin ) );
+        CHECK( true  == ( end >= iter ) );
+        CHECK( false == ( begin >= end ) );
+      } // THEN
+    } // WHEN
+  } // GIVEN
+} // SCENARIO