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include/tl/algorithm/append.h

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+#pragma once
+
+#include "tl/detail/prologue.h"
+#include "tl/type_traits.h"
+
+#include <iterator>
+#include <type_traits>
+#include <forward_list>
+
+namespace tl
+{
+namespace detail
+{
+//////////////////////////////////////////////////////////////////////////
+
+// associative containers (ordered & unordered) [maps, unordered_maps, multimaps, unordered_multimaps ...]
+template <typename SrcContainer, typename DstContainer>
+void append(std::true_type, DstContainer& dst, const SrcContainer& src) noexcept
+{
+	dst.insert(std::begin(src), std::end(src));
+}
+//////////////////////////////////////////////////////////////////////////
+
+// sequence containers [vector, dequeue, forward_list, list, ...]
+template <typename SrcContainer, typename DstContainer>
+void append(std::false_type, DstContainer& dst, const SrcContainer& src) noexcept
+{
+	dst.insert(std::end(dst), std::begin(src), std::end(src));
+}
+
+//////////////////////////////////////////////////////////////////////////
+
+// Obs: std::forward_list don't support fast traversal to the end 
+//      thus going to std::prev(std::end(dst)) must be done manually
+// Cost: O(N)
+template <typename T, typename SrcContainer>
+void append(std::false_type, std::forward_list<T>& dst, const SrcContainer& src) noexcept
+{
+	auto before_end = dst.before_begin();
+	for (auto& _ : dst)
+		++before_end;
+
+	dst.insert_after(before_end, std::begin(src), std::end(src));
+}
+
+//////////////////////////////////////////////////////////////////////////
+} // namespace detail
+
+  //////////////////////////////////////////////////////////////////////////
+
+template <typename SrcContainer, typename DstContainer>
+void append(DstContainer& dst, const SrcContainer& src) noexcept
+{
+	detail::append(tl::is_associative_container<DstContainer>{}, dst, src);
+}
+
+//////////////////////////////////////////////////////////////////////////
+
+}