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61 lines
2.1 KiB
C++
61 lines
2.1 KiB
C++
#pragma once
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#include <ext/size.h>
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#include <type_traits>
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#include <utility>
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#include <iterator>
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/** \brief Provides a wrapper view around a container, allowing to iterate over it's elements and indices.
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* Allow writing code like shown below:
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*
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* std::vector<T> v = getVector();
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* for (const std::pair<const std::size_t, T &> index_and_value : ext::enumerate(v))
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* std::cout << "element " << index_and_value.first << " is " << index_and_value.second << std::endl;
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*/
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namespace ext
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{
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template <typename It> struct enumerate_iterator
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{
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using traits = typename std::iterator_traits<It>;
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using iterator_category = typename traits::iterator_category;
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using value_type = std::pair<const std::size_t, typename traits::value_type>;
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using difference_type = typename traits::difference_type;
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using reference = std::pair<const std::size_t, typename traits::reference>;
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std::size_t idx;
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It it;
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enumerate_iterator(const std::size_t idx, It it) : idx{idx}, it{it} {}
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auto operator*() const { return reference(idx, *it); }
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bool operator!=(const enumerate_iterator & other) const { return it != other.it; }
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enumerate_iterator & operator++() { return ++idx, ++it, *this; }
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};
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template <typename Collection> struct enumerate_wrapper
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{
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using underlying_iterator = decltype(std::begin(std::declval<Collection &>()));
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using iterator = enumerate_iterator<underlying_iterator>;
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Collection & collection;
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enumerate_wrapper(Collection & collection) : collection(collection) {}
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auto begin() { return iterator(0, std::begin(collection)); }
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auto end() { return iterator(ext::size(collection), std::end(collection)); }
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};
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template <typename Collection> auto enumerate(Collection & collection)
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{
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return enumerate_wrapper<Collection>{collection};
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}
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template <typename Collection> auto enumerate(const Collection & collection)
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{
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return enumerate_wrapper<const Collection>{collection};
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}
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}
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