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[ADT] Add a generic iterator utility for adapting iterators much like
Boost's iterator_adaptor, and a specific adaptor which iterates over pointees when wrapped around an iterator over pointers. This is the result of a long discussion on IRC with Duncan Smith, Dave Blaikie, Richard Smith, and myself. Essentially, I could use some subset of the iterator facade facilities often used from Boost, and everyone seemed interested in having the functionality in a reasonably generic form. I've tried to strike a balance between the pragmatism and the established Boost design. The primary differences are: 1) Delegating to the standard iterator interface names rather than special names that then make up a second iterator-like API. 2) Using the name 'pointee_iterator' which seems more clear than 'indirect_iterator'. The whole business of calling the '*p' operation 'pointer indirection' in the standard is ... quite confusing. And 'dereference' is no better of a term for moving from a pointer to a reference. Hoping Duncan, and others continue to provide comments on this until we've got a nice, minimal abstraction. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207069 91177308-0d34-0410-b5e6-96231b3b80d8
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include/llvm/ADT/iterator.h
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include/llvm/ADT/iterator.h
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//===- iterator.h - Utilities for using and defining iterators --*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_ITERATOR_H
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#define LLVM_ADT_ITERATOR_H
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#include <iterator>
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namespace llvm {
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/// \brief CRTP base class for adapting an iterator to a different type.
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///
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/// This class can be used through CRTP to adapt one iterator into another.
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/// Typically this is done through providing in the derived class a custom \c
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/// operator* implementation. Other methods can be overridden as well.
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///
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/// FIXME: Factor out the iterator-facade-like aspects into a base class that
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/// can be used for defining completely custom iterators.
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template <typename DerivedT, typename WrappedIteratorT, typename T,
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typename PointerT = T *, typename ReferenceT = T &,
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// Don't provide these, they are mostly to act as aliases below.
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typename WrappedTraitsT = std::iterator_traits<WrappedIteratorT>>
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class iterator_adaptor_base
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: public std::iterator<typename WrappedTraitsT::iterator_category, T,
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typename WrappedTraitsT::difference_type, PointerT,
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ReferenceT> {
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protected:
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WrappedIteratorT I;
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iterator_adaptor_base() {}
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template <
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typename U,
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typename = typename std::enable_if<
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!std::is_same<typename std::remove_cv<
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typename std::remove_reference<U>::type>::type,
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DerivedT>::value>::type>
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explicit iterator_adaptor_base(U &&u)
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: I(std::forward<U &&>(u)) {}
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public:
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typedef typename iterator_adaptor_base::iterator::difference_type
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difference_type;
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DerivedT &operator+=(difference_type n) {
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I += n;
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return *static_cast<DerivedT *>(this);
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}
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DerivedT &operator-=(difference_type n) {
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I -= n;
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return *static_cast<DerivedT *>(this);
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}
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DerivedT operator+(difference_type n) const {
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DerivedT tmp = *this;
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tmp += n;
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return tmp;
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}
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friend DerivedT operator+(difference_type n, const DerivedT &i) {
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return i + n;
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}
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DerivedT operator-(difference_type n) const {
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DerivedT tmp = *this;
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tmp -= n;
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return tmp;
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}
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difference_type operator-(const DerivedT &RHS) const { return I - RHS.I; }
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DerivedT &operator++() {
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++I;
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return *static_cast<DerivedT *>(this);
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}
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DerivedT &operator--() {
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--I;
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return *static_cast<DerivedT *>(this);
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}
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DerivedT operator++(int) {
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DerivedT tmp = *static_cast<DerivedT *>(this);
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++*this;
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return tmp;
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}
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DerivedT operator--(int) {
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DerivedT tmp = *static_cast<DerivedT *>(this);
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--*this;
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return tmp;
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}
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bool operator==(const DerivedT &RHS) const { return I == RHS.I; }
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bool operator!=(const DerivedT &RHS) const {
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return !static_cast<const DerivedT *>(this)->operator==(RHS);
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}
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bool operator<(const DerivedT &RHS) const { return I < RHS.I; }
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bool operator>(const DerivedT &RHS) const {
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return !static_cast<const DerivedT *>(this)->operator<(RHS) &&
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!static_cast<const DerivedT *>(this)->operator==(RHS);
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}
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bool operator<=(const DerivedT &RHS) const {
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return !static_cast<const DerivedT *>(this)->operator>(RHS);
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}
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bool operator>=(const DerivedT &RHS) const {
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return !static_cast<const DerivedT *>(this)->operator<(RHS);
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}
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ReferenceT operator*() const { return *I; }
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PointerT operator->() const {
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return static_cast<const DerivedT *>(this)->operator*();
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}
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ReferenceT operator[](difference_type n) const {
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return *static_cast<const DerivedT *>(this)->operator+(n);
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}
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};
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/// \brief An iterator type that allows iterating over the pointees via some
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/// other iterator.
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///
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/// The typical usage of this is to expose a type that iterates over Ts, but
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/// which is implemented with some iterator over T*s:
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///
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/// \code
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/// typedef pointee_iterator<SmallVectorImpl<T *>::iterator> iterator;
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/// \endcode
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template <
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typename WrappedIteratorT,
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typename T = typename std::remove_pointer<
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typename std::iterator_traits<WrappedIteratorT>::value_type>::type>
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struct pointee_iterator
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: iterator_adaptor_base<pointee_iterator<WrappedIteratorT>,
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WrappedIteratorT, T> {
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pointee_iterator() {}
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template <typename U>
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pointee_iterator(U &&u)
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: pointee_iterator::iterator_adaptor_base(std::forward<U &&>(u)) {}
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T &operator*() const { return **this->I; }
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};
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}
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#endif
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@ -15,12 +15,13 @@ add_llvm_unittest(SupportTests
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EndianTest.cpp
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ErrorOrTest.cpp
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FileOutputBufferTest.cpp
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IteratorTest.cpp
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LEB128Test.cpp
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LineIteratorTest.cpp
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LockFileManagerTest.cpp
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MD5Test.cpp
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ManagedStatic.cpp
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MathExtrasTest.cpp
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MD5Test.cpp
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MemoryBufferTest.cpp
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MemoryTest.cpp
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Path.cpp
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59
unittests/Support/IteratorTest.cpp
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unittests/Support/IteratorTest.cpp
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//===- IteratorTest.cpp - Unit tests for iterator utilities ---------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/iterator.h"
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#include "llvm/ADT/SmallVector.h"
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#include "gtest/gtest.h"
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using namespace llvm;
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namespace {
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TEST(PointeeIteratorTest, Basic) {
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int arr[4] = { 1, 2, 3, 4 };
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SmallVector<int *, 4> V;
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V.push_back(&arr[0]);
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V.push_back(&arr[1]);
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V.push_back(&arr[2]);
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V.push_back(&arr[3]);
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typedef pointee_iterator<SmallVectorImpl<int *>::const_iterator> test_iterator;
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test_iterator Begin, End;
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Begin = V.begin();
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End = test_iterator(V.end());
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test_iterator I = Begin;
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for (int i = 0; i < 4; ++i) {
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EXPECT_EQ(*V[i], *I);
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EXPECT_EQ(I, Begin + i);
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EXPECT_EQ(I, std::next(Begin, i));
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test_iterator J = Begin;
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J += i;
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EXPECT_EQ(I, J);
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EXPECT_EQ(*V[i], Begin[i]);
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EXPECT_NE(I, End);
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EXPECT_GT(End, I);
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EXPECT_LT(I, End);
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EXPECT_GE(I, Begin);
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EXPECT_LE(Begin, I);
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EXPECT_EQ(i, I - Begin);
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EXPECT_EQ(i, std::distance(Begin, I));
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EXPECT_EQ(Begin, I - i);
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test_iterator K = I++;
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EXPECT_EQ(K, std::prev(I));
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}
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EXPECT_EQ(End, I);
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}
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} // anonymous namespace
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