refs #290 using a CRange of iterator adaptors to return from the primary predicate-based methods of CRangeBase without copying elements

src/blackmisc/collection.h

@@ -42,7 +42,7 @@ namespace BlackMisc
      * Can take any suitable container class as its implementation at runtime.
      */
     template <class T>
-    class CCollection : public CContainerBase<CCollection, T>
+    class CCollection : public CContainerBase<CCollection, T, Iterators::ConstForwardIterator<T>>
     {
     public:
         //! \brief STL compatibility

src/blackmisc/containerbase.h

@@ -45,8 +45,8 @@ namespace BlackMisc
     /*!
      * \brief Base class for CCollection and CSequence adding mutating operations and CValueObject facility on top of CRangeBase.
      */
-    template <template <class> class C, class T>
-    class CContainerBase : public CValueObject, public CRangeBase<C<T>, T>
+    template <template <class> class C, class T, class CIt>
+    class CContainerBase : public CValueObject, public CRangeBase<C<T>, CIt>
     {
     public:
         /*!

src/blackmisc/range.h

@@ -8,34 +8,42 @@
 #ifndef BLACKMISC_RANGE_H
 #define BLACKMISC_RANGE_H
 
-#include "valueobject.h"
 #include "indexvariantmap.h"
+#include "iterator.h"
 #include "predicates.h"
-#include "json.h"
+#include <QtGlobal>
 #include <algorithm>
+#include <type_traits>
+#include <iterator>
 
 namespace BlackMisc
 {
 
+    template <class> class CRange;
+
     /*!
      * Any container class with begin and end iterators can inherit from this CRTP class
      * to gain some useful algorithms as member functions.
      * \tparam Derived The most derived container class inheriting from this instantiation.
+     * \tparam CIt the const_iterator of Derived.
      */
-    template <class Derived, class T>
+    template <class Derived, class CIt>
     class CRangeBase
     {
     public:
+        /*!
+         * Return a new container generated by applying some transformation function to all elements of this one.
+         */
+        template <class F>
+        inline auto transform(F function) const
+            -> CRange<Iterators::TransformIterator<CIt, F>>;
+
         /*!
          * \brief Return a copy containing only those elements for which a given predicate returns true.
          */
         template <class Predicate>
-        Derived findBy(Predicate p) const
-        {
-            Derived result = derived();
-            result.erase(std::remove_if(result.begin(), result.end(), [ = ](const typename Derived::value_type & value) { return !p(value); }), result.end());
-            return result;
-        }
+        inline auto findBy(Predicate p) const
+            -> CRange<Iterators::ConditionalIterator<CIt, Predicate>>;
 
         /*!
          * \brief Return a copy containing only those elements matching some particular key/value pair(s).
@@ -44,31 +52,28 @@ namespace BlackMisc
          * \param keysValues Zero or more additional pairs of { pointer to member function of T, value to compare it against }.
          */
         template <class K0, class V0, class... KeysValues>
-        Derived findBy(K0 k0, V0 v0, KeysValues... keysValues) const
-        {
-            return findBy(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...));
-        }
+        inline auto findBy(K0 k0, V0 v0, KeysValues... keysValues) const
+            -> CRange<Iterators::ConditionalIterator<CIt, decltype(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...))>>;
 
         /*!
          * \brief Return a copy containing only those elements matching a given value map.
          */
-        Derived findBy(const CIndexVariantMap &valueMap) const
-        {
-            return findBy([ & ](const T & value) { return value == valueMap; });
-        }
+        inline auto findBy(CIndexVariantMap valueMap) const
+            -> CRange<Iterators::ConditionalIterator<CIt, decltype(BlackMisc::Predicates::Equals(std::move(valueMap)))>>;
 
         /*!
          * \brief Return true if there is an element for which a given predicate returns true.
          */
         template <class Predicate>
-        bool contains(Predicate p) const
+        bool containsBy(Predicate p) const
         {
             return std::any_of(derived().cbegin(), derived().cend(), p);
         }
 
         /*!
-         * \brief Return true if there is an element equal to given object. Uses the most efficient implementation available.
+         * \brief Return true if there is an element equal to given object. Uses the most efficient implementation available in the derived container.
          */
+        template <class T>
         bool contains(const T &object) const
         {
             return derived().find(object) != derived().cend();
@@ -83,7 +88,7 @@ namespace BlackMisc
         template <class K0, class V0, class... KeysValues>
         bool contains(K0 k0, V0 v0, KeysValues... keysValues) const
         {
-            return contains(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...));
+            return containsBy(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...));
         }
 
     private:
@@ -102,7 +107,7 @@ namespace BlackMisc
      *          during the lifetime of the range.
      */
     template <class I>
-    class CRange : public CRangeBase<CRange<I>, typename std::iterator_traits<I>::value_type>
+    class CRange : public CRangeBase<CRange<I>, I>
     {
     public:
         //! STL compatibility
@@ -213,6 +218,40 @@ namespace BlackMisc
         return { container.cbegin(), container.cend() };
     }
 
+    /*
+     * Member functions of CRangeBase template defined out of line, because they depend on CRange etc.
+     */
+    template <class Derived, class CIt>
+    template <class F>
+    auto CRangeBase<Derived, CIt>::transform(F function) const
+        -> CRange<Iterators::TransformIterator<CIt, F>>
+    {
+        return makeRange(Iterators::makeTransformIterator(derived().cbegin(), function), derived().cend());
+    }
+
+    template <class Derived, class CIt>
+    template <class Predicate>
+    auto CRangeBase<Derived, CIt>::findBy(Predicate p) const
+        -> CRange<Iterators::ConditionalIterator<CIt, Predicate>>
+    {
+        return makeRange(makeConditionalIterator(derived().cbegin(), derived().cend(), p), derived().cend());
+    }
+
+    template <class Derived, class CIt>
+    template <class K0, class V0, class... KeysValues>
+    auto CRangeBase<Derived, CIt>::findBy(K0 k0, V0 v0, KeysValues... keysValues) const
+        -> CRange<Iterators::ConditionalIterator<CIt, decltype(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...))>>
+    {
+        return findBy(BlackMisc::Predicates::MemberEqual(k0, v0, keysValues...));
+    }
+
+    template <class Derived, class CIt>
+    auto CRangeBase<Derived, CIt>::findBy(CIndexVariantMap valueMap) const
+        -> CRange<Iterators::ConditionalIterator<CIt, decltype(BlackMisc::Predicates::Equals(std::move(valueMap)))>>
+    {
+        return findBy(BlackMisc::Predicates::Equals(std::move(valueMap)));
+    }
+
 }
 
 #endif // guard

src/blackmisc/sequence.h

@@ -28,7 +28,7 @@ namespace BlackMisc
      * Can take any suitable container class as its implementation at runtime.
      */
     template <class T>
-    class CSequence : public CContainerBase<CSequence, T>
+    class CSequence : public CContainerBase<CSequence, T, Iterators::ConstBidirectionalIterator<T>>
     {
     public:
         //! \brief STL compatibility