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include/boost/algorithm/cxx17/transform_inclusive_scan.hpp

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+/*
+   Copyright (c) Marshall Clow 2017.
+
+   Distributed under the Boost Software License, Version 1.0. (See accompanying
+   file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+*/
+
+/// \file  transform_reduce.hpp
+/// \brief Combine the (transformed) elements of a sequence (or two) into a single value.
+/// \author Marshall Clow
+
+#ifndef BOOST_ALGORITHM_TRANSFORM_REDUCE_HPP
+#define BOOST_ALGORITHM_TRANSFORM_REDUCE_HPP
+
+#include <functional>     // for std::plus
+#include <iterator>       // for std::iterator_traits
+
+#include <boost/config.hpp>
+#include <boost/range/begin.hpp>
+#include <boost/range/end.hpp>
+#include <boost/range/value_type.hpp>
+
+namespace boost { namespace algorithm {
+
+/// \fn transform_inclusive_scan ( InputIterator first, InputIterator last, OutputIterator result, BinaryOperation bOp, UnaryOperation uOp, T init )
+/// \brief Transforms elements from the input range with uOp and then combines
+/// those transformed elements with bOp such that the n-1th element and the nth
+/// element are combined. Inclusivity means that the nth element is included in
+/// the nth combination.
+/// \return The updated output iterator
+///
+/// \param first  The start of the input sequence
+/// \param last   The end of the input sequence
+/// \param result The output iterator to write the results into
+/// \param bOp    The operation for combining transformed input elements
+/// \param uOp    The operation for transforming input elements
+/// \param init   The initial value
+///
+/// \note This function is part of the C++17 standard library
+template<class InputIterator, class OutputIterator,
+         class BinaryOperation, class UnaryOperation, class T>
+OutputIterator transform_inclusive_scan(InputIterator first, InputIterator last,
+                                        OutputIterator result,
+                                        BinaryOperation bOp, UnaryOperation uOp,
+                                        T init)
+{
+    for (; first != last; ++first, (void) ++result) {
+        init = bOp(init, uOp(*first));
+        *result = init;
+        }
+
+    return result;
+}
+
+/// \fn transform_inclusive_scan ( InputIterator first, InputIterator last, OutputIterator result, BinaryOperation bOp, UnaryOperation uOp, T init )
+/// \brief Transforms elements from the input range with uOp and then combines
+/// those transformed elements with bOp such that the n-1th element and the nth
+/// element are combined. Inclusivity means that the nth element is included in
+/// the nth combination. The first value will be used as the init.
+/// \return The updated output iterator
+///
+/// \param first  The start of the input sequence
+/// \param last   The end of the input sequence
+/// \param result The output iterator to write the results into
+/// \param bOp    The operation for combining transformed input elements
+/// \param uOp    The operation for transforming input elements
+///
+/// \note This function is part of the C++17 standard library
+template<class InputIterator, class OutputIterator,
+         class BinaryOperation, class UnaryOperation>
+OutputIterator transform_inclusive_scan(InputIterator first, InputIterator last,
+                                        OutputIterator result,
+                                        BinaryOperation bOp, UnaryOperation uOp)
+{
+    if (first != last) {
+        typename std::iterator_traits<InputIterator>::value_type init = uOp(*first);
+        *result++ = init;
+        if (++first != last)
+            return boost::algorithm::transform_inclusive_scan
+                                              (first, last, result, bOp, uOp, init);
+        }
+
+    return result;
+}
+
+
+}} // namespace boost and algorithm
+
+#endif // BOOST_ALGORITHM_TRANSFORM_REDUCE_HPP