From 06be3ec6c9e821320b09592aea781830612df2aa Mon Sep 17 00:00:00 2001
From: Vasileios Karakasis <vkarak@gmail.com>
Date: Tue, 13 Dec 2016 10:29:19 +0100
Subject: [PATCH] Cyclic iterators and cyclic range views (#119)
Add cyclic iterators and cyclic range view.
Cyclic iterators wrap around when the reach the end of the underlying range over which they are defined.
---
src/util/cycle.hpp | 210 +++++++++++++++++++++++++++++++++++++
tests/unit/CMakeLists.txt | 1 +
tests/unit/test_cycle.cpp | 211 ++++++++++++++++++++++++++++++++++++++
3 files changed, 422 insertions(+)
create mode 100644 src/util/cycle.hpp
create mode 100644 tests/unit/test_cycle.cpp
diff --git a/src/util/cycle.hpp b/src/util/cycle.hpp
new file mode 100644
index 00000000..a4405bdb
--- /dev/null
+++ b/src/util/cycle.hpp
@@ -0,0 +1,210 @@
+#pragma once
+
+#include <utility>
+#include <util/iterutil.hpp>
+#include <util/range.hpp>
+
+namespace nest {
+namespace mc {
+namespace util {
+
+template <typename I, typename S = I>
+class cyclic_iterator : public iterator_adaptor<cyclic_iterator<I,S>, I> {
+ using base = iterator_adaptor<cyclic_iterator<I,S>, I>;
+ friend class iterator_adaptor<cyclic_iterator<I,S>, I>;
+
+ I begin_;
+ I inner_;
+ S end_;
+ typename base::difference_type off_; // offset from begin
+
+ const I& inner() const {
+ return inner_;
+ }
+
+ I& inner() {
+ return inner_;
+ }
+
+public:
+ using value_type = typename base::value_type;
+ using difference_type = typename base::difference_type;
+
+ cyclic_iterator() = default;
+
+ template <typename Iter, typename Sentinel>
+ cyclic_iterator(Iter&& iter, Sentinel&& sentinel)
+ : begin_(std::forward<Iter>(iter)),
+ inner_(std::forward<Iter>(iter)),
+ end_(std::forward<Sentinel>(sentinel)),
+ off_(0)
+ { }
+
+ cyclic_iterator(const cyclic_iterator& other)
+ : begin_(other.begin_),
+ inner_(other.inner_),
+ end_(other.end_),
+ off_(other.off_)
+ { }
+
+ cyclic_iterator(cyclic_iterator&& other)
+ : begin_(std::move(other.begin_)),
+ inner_(std::move(other.inner_)),
+ end_(std::move(other.end_)),
+ off_(other.off_)
+ { }
+
+
+ cyclic_iterator& operator=(const cyclic_iterator& other) {
+ if (this != &other) {
+ inner_ = other.inner_;
+ begin_ = other.begin_;
+ end_ = other.end_;
+ off_ = other.off_;
+ }
+
+ return *this;
+ }
+
+ cyclic_iterator& operator=(cyclic_iterator&& other) {
+ if (this != &other) {
+ inner_ = std::move(other.inner_);
+ begin_ = std::move(other.begin_);
+ end_ = std::move(other.end_);
+ off_ = other.off_;
+ }
+
+ return *this;
+ }
+
+ // forward and input iterator requirements
+ value_type operator*() const {
+ return *inner_;
+ }
+
+ value_type operator[](difference_type n) const {
+ return *(*this + n);
+ }
+
+ cyclic_iterator& operator++() {
+ if (++inner_ == end_) {
+ // wrap around
+ inner_ = begin_;
+ }
+
+ ++off_;
+ return *this;
+ }
+
+ cyclic_iterator operator++(int) {
+ cyclic_iterator iter(*this);
+ ++(*this);
+ return iter;
+ }
+
+ cyclic_iterator& operator--() {
+ if (inner_ == begin_) {
+ // wrap around; use upto() to handle efficiently the move to the end
+ // in case inner_ is a bidirectional iterator
+ inner_ = upto(inner_, end_);
+ }
+ else {
+ --inner_;
+ }
+
+ --off_;
+ return *this;
+ }
+
+ cyclic_iterator operator--(int) {
+ cyclic_iterator iter(*this);
+ --(*this);
+ return iter;
+ }
+
+ cyclic_iterator& operator+=(difference_type n) {
+ // wrap distance
+ auto size = util::distance(begin_, end_);
+
+ // calculate distance from begin
+ auto pos = (off_ += n);
+ if (pos < 0) {
+ auto mod = -pos % size;
+ pos = mod ? size - mod : 0;
+ }
+ else {
+ pos = pos % size;
+ }
+
+ inner_ = std::next(begin_, pos);
+ return *this;
+ }
+
+ cyclic_iterator& operator-=(difference_type n) {
+ return this->operator+=(-n);
+ }
+
+ bool operator==(const cyclic_iterator& other) const {
+ return begin_ == other.begin_ && off_ == other.off_;
+ }
+
+ bool operator!=(const cyclic_iterator& other) const {
+ return !(*this == other);
+ }
+
+ cyclic_iterator operator-(difference_type n) const {
+ cyclic_iterator c(*this);
+ return c -= n;
+ }
+
+ difference_type operator-(const cyclic_iterator& other) const {
+ return off_ - other.off_;
+ }
+
+ bool operator<(const cyclic_iterator& other) const {
+ return off_ < other.off_;
+ }
+
+ // expose inner iterator for testing against a sentinel
+ template <typename Sentinel>
+ bool operator==(const Sentinel& s) const {
+ return inner_ == s;
+ }
+
+ template <typename Sentinel>
+ bool operator!=(const Sentinel& s) const {
+ return !(inner_ == s);
+ }
+};
+
+template <typename I, typename S>
+cyclic_iterator<I, S> make_cyclic_iterator(const I& iter, const S& sentinel) {
+ return cyclic_iterator<I, S>(iter, sentinel);
+}
+
+
+template <
+ typename Seq,
+ typename SeqIter = typename sequence_traits<Seq>::const_iterator,
+ typename SeqSentinel = typename sequence_traits<Seq>::const_sentinel,
+ typename = enable_if_t<std::is_same<SeqIter, SeqSentinel>::value>
+>
+range<cyclic_iterator<SeqIter, SeqSentinel> > cyclic_view(const Seq& s) {
+ return { make_cyclic_iterator(cbegin(s), cend(s)),
+ make_cyclic_iterator(cend(s), cend(s)) };
+}
+
+template <
+ typename Seq,
+ typename SeqIter = typename sequence_traits<Seq>::const_iterator,
+ typename SeqSentinel = typename sequence_traits<Seq>::const_sentinel,
+ typename = enable_if_t<!std::is_same<SeqIter, SeqSentinel>::value>
+>
+range<cyclic_iterator<SeqIter, SeqSentinel>, SeqSentinel>
+cyclic_view(const Seq& s) {
+ return { make_cyclic_iterator(cbegin(s), cend(s)), cend(s) };
+}
+
+} // namespace util
+} // namespace mc
+} // namespace nest
diff --git a/tests/unit/CMakeLists.txt b/tests/unit/CMakeLists.txt
index 75c46c46..45de9716 100644
--- a/tests/unit/CMakeLists.txt
+++ b/tests/unit/CMakeLists.txt
@@ -14,6 +14,7 @@ set(TEST_SOURCES
test_cell.cpp
test_compartments.cpp
test_counter.cpp
+ test_cycle.cpp
test_either.cpp
test_event_queue.cpp
test_filter.cpp
diff --git a/tests/unit/test_cycle.cpp b/tests/unit/test_cycle.cpp
new file mode 100644
index 00000000..d022a666
--- /dev/null
+++ b/tests/unit/test_cycle.cpp
@@ -0,0 +1,211 @@
+#include "../gtest.h"
+
+#include <algorithm>
+#include <iterator>
+#include <string>
+
+#include "common.hpp"
+#include <util/cycle.hpp>
+#include <util/meta.hpp>
+
+using namespace nest::mc;
+
+TEST(cycle_iterator, construct) {
+ std::vector<int> values = { 4, 2, 3 };
+ auto cycle_iter = util::make_cyclic_iterator(values.cbegin(), values.cend());
+
+ {
+ // copy constructor
+ auto cycle_iter_copy(cycle_iter);
+ EXPECT_EQ(cycle_iter, cycle_iter_copy);
+ }
+
+ {
+ // copy assignment
+ auto cycle_iter_copy = cycle_iter;
+ EXPECT_EQ(cycle_iter, cycle_iter_copy);
+ }
+
+ {
+ // move constructor
+ auto cycle_iter_copy(
+ util::make_cyclic_iterator(values.cbegin(), values.cend())
+ );
+ EXPECT_EQ(cycle_iter, cycle_iter_copy);
+ }
+}
+
+
+TEST(cycle_iterator, increment) {
+ std::vector<int> values = { 4, 2, 3 };
+
+ {
+ // test operator++
+ auto cycle_iter = util::make_cyclic_iterator(values.cbegin(),
+ values.cend());
+ auto cycle_iter_copy = cycle_iter;
+
+ auto values_size = values.size();
+ for (auto i = 0u; i < 2*values_size; ++i) {
+ EXPECT_EQ(values[i % values_size], *cycle_iter);
+ EXPECT_EQ(values[i % values_size], *cycle_iter_copy++);
+ ++cycle_iter;
+ }
+ }
+
+ {
+ // test operator[]
+ auto cycle_iter = util::make_cyclic_iterator(values.cbegin(),
+ values.cend());
+
+ for (auto i = 0u; i < values.size(); ++i) {
+ EXPECT_EQ(values[i], cycle_iter[values.size() + i]);
+ }
+ }
+
+ {
+ auto cycle_iter = util::make_cyclic_iterator(values.cbegin(),
+ values.cend());
+ EXPECT_NE(cycle_iter + 1, cycle_iter + 10);
+ }
+}
+
+TEST(cycle_iterator, decrement) {
+ std::vector<int> values = { 4, 2, 3 };
+
+ {
+ // test operator--
+ auto cycle_iter = util::make_cyclic_iterator(values.cbegin(),
+ values.cend());
+ auto cycle_iter_copy = cycle_iter;
+
+ auto values_size = values.size();
+ for (auto i = 0u; i < 2*values_size; ++i) {
+ --cycle_iter;
+ cycle_iter_copy--;
+ auto val = values[values_size - i%values_size - 1];
+ EXPECT_EQ(val, *cycle_iter);
+ EXPECT_EQ(val, *cycle_iter_copy);
+ }
+ }
+
+ {
+ // test operator[]
+ auto cycle_iter = util::make_cyclic_iterator(values.cbegin(),
+ values.cend());
+ int values_size = values.size();
+ for (int i = 0; i < 2*values_size; ++i) {
+ auto pos = i % values_size;
+ pos = pos ? values_size - pos : 0;
+ EXPECT_EQ(values[pos], cycle_iter[-i]);
+ }
+ }
+
+ {
+ auto cycle_iter = util::make_cyclic_iterator(values.cbegin(),
+ values.cend());
+ EXPECT_NE(cycle_iter - 2, cycle_iter - 5);
+ EXPECT_NE(cycle_iter + 1, cycle_iter - 5);
+ }
+}
+
+TEST(cycle_iterator, carray) {
+ int values[] = { 4, 2, 3 };
+ auto cycle_iter = util::make_cyclic_iterator(util::cbegin(values),
+ util::cend(values));
+ auto values_size = util::size(values);
+ for (auto i = 0u; i < 2*values_size; ++i) {
+ EXPECT_EQ(values[i % values_size], *cycle_iter++);
+ }
+}
+
+TEST(cycle_iterator, sentinel) {
+ using testing::null_terminated;
+
+ auto msg = "hello";
+ auto cycle_iter = util::make_cyclic_iterator(msg, null_terminated);
+
+ auto msg_len = std::string(msg).size();
+ for (auto i = 0u; i < 2*msg_len; ++i) {
+ EXPECT_EQ(msg[i % msg_len], *cycle_iter++);
+ }
+}
+
+
+TEST(cycle, cyclic_view) {
+ std::vector<int> values = { 4, 2, 3 };
+ std::vector<int> values_new;
+
+ std::copy_n(util::cyclic_view(values).cbegin(), 10,
+ std::back_inserter(values_new));
+
+ EXPECT_EQ(10u, values_new.size());
+
+ auto i = 0;
+ for (auto const& v : values_new) {
+ EXPECT_EQ(values[i++ % values.size()], v);
+ }
+}
+
+TEST(cycle_iterator, difference) {
+ int values[] = { 4, 2, 3 };
+
+ auto cycle = util::cyclic_view(values);
+ auto c1 = cycle.begin();
+
+ auto c2 = c1;
+ EXPECT_EQ(0, c2-c1);
+
+ ++c2;
+ EXPECT_EQ(1, c2-c1);
+
+ ++c1;
+ EXPECT_EQ(0, c2-c1);
+
+ c2 += 6;
+ EXPECT_EQ(6, c2-c1);
+
+ c1 += 2;
+ EXPECT_EQ(4, c2-c1);
+
+ --c2;
+ EXPECT_EQ(3, c2-c1);
+
+ c1 -= 3;
+ EXPECT_EQ(6, c2-c1);
+}
+
+TEST(cycle_iterator, order) {
+ int values[] = { 4, 2, 3 };
+
+ auto cycle = util::cyclic_view(values);
+ auto c1 = cycle.begin();
+ auto c2 = c1;
+
+ EXPECT_FALSE(c1 < c2);
+ EXPECT_FALSE(c2 < c1);
+ EXPECT_TRUE(c1 <= c2);
+ EXPECT_TRUE(c1 >= c2);
+
+ c2 += util::size(values);
+
+ EXPECT_TRUE(c1 < c2);
+ EXPECT_FALSE(c2 < c1);
+ EXPECT_TRUE(c1 <= c2);
+ EXPECT_FALSE(c1 >= c2);
+}
+
+TEST(cycle, cyclic_view_sentinel) {
+ const char *msg = "hello";
+ auto cycle = util::cyclic_view(
+ util::make_range(msg, testing::null_terminated)
+ );
+
+ std::string msg_new;
+ auto msg_new_size = 2*std::string(msg).size();
+ for (auto i = 0u; i < msg_new_size; ++i) {
+ msg_new += cycle[i];
+ }
+
+ EXPECT_EQ("hellohello", msg_new);
+}
--
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