On Mon, 19 May 2025, Tomasz Kaminski wrote:
>
>
> On Mon, May 19, 2025 at 9:59 AM Tomasz Kaminski <tkami...@redhat.com> wrote:
>
>
> On Mon, May 19, 2025 at 6:47 AM Patrick Palka <ppa...@redhat.com> wrote:
> I would appreciate a short explanation on the approach being put here,
> in the message. Like passing -1 as means of saying, size not know.
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
>
> From the non-stylistic changes, I have noticed that we need some explicit
> conversion between different types.
> I think we should add test that would check with size being __max_diff_t,
> maybe we should add such a range to
> testutils_iterators.
> Rest of the of comments are mostly stylistic.
>
>
> -- >8 --
>
> libstdc++-v3/ChangeLog:
>
> * include/bits/ranges_algo.h (__starts_with_fn, starts_with):
> Define.
> (__ends_with_fn, ends_with): Define.
> * include/bits/version.def (ranges_starts_ends_with): Define.
> * include/bits/version.h: Regenerate.
> * include/std/algorithm: Provide
> __cpp_lib_ranges_starts_ends_with.
> * src/c++23/std.cc.in (ranges::starts_with): Export.
> (ranges::ends_with): Export.
> * testsuite/25_algorithms/ends_with/1.cc: New test.
> * testsuite/25_algorithms/starts_with/1.cc: New test.
> ---
> libstdc++-v3/include/bits/ranges_algo.h | 232 ++++++++++++++++++
> libstdc++-v3/include/bits/version.def | 8 +
> libstdc++-v3/include/bits/version.h | 10 +
> libstdc++-v3/include/std/algorithm | 1 +
> libstdc++-v3/src/c++23/std.cc.in | 4 +
> .../testsuite/25_algorithms/ends_with/1.cc | 129 ++++++++++
> .../testsuite/25_algorithms/starts_with/1.cc | 128 ++++++++++
> 7 files changed, 512 insertions(+)
> create mode 100644 libstdc++-v3/testsuite/25_algorithms/ends_with/1.cc
> create mode 100644
> libstdc++-v3/testsuite/25_algorithms/starts_with/1.cc
>
> diff --git a/libstdc++-v3/include/bits/ranges_algo.h
> b/libstdc++-v3/include/bits/ranges_algo.h
> index f36e7dd59911..c59a555f528a 100644
> --- a/libstdc++-v3/include/bits/ranges_algo.h
> +++ b/libstdc++-v3/include/bits/ranges_algo.h
> @@ -438,6 +438,238 @@ namespace ranges
>
> inline constexpr __search_n_fn search_n{};
>
> +#if __glibcxx_ranges_starts_ends_with // C++ >= 23
> + struct __starts_with_fn
> + {
> + template<input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
> + input_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
> + typename _Pred = ranges::equal_to,
> + typename _Proj1 = identity, typename _Proj2 = identity>
> + requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1,
> _Proj2>
> + constexpr bool
> + operator()(_Iter1 __first1, _Sent1 __last1,
> + _Iter2 __first2, _Sent2 __last2, _Pred __pred = {},
> + _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const
> + {
>
> We could check __first == __last2 early here, before even computing size.
Hmm, computing the size should be very cheap though? I'm not sure this
first would be worthwhile since an empty needle is a very uncommon case.
> + iter_difference_t<_Iter1> __n1 = -1;
> + iter_difference_t<_Iter2> __n2 = -1;
> + if constexpr (sized_sentinel_for<_Sent1, _Iter1>)
> + __n1 = __last1 - __first1;
> + if constexpr (sized_sentinel_for<_Sent2, _Iter2>)
> + __n2 = __last2 - __first2;
> + return _S_impl(std::move(__first1), __last1,
> + std::move(__first2), __last2,
> + std::move(__pred),
> + std::move(__proj1), std::move(__proj2),
> + __n1, __n2);
> + }
> +
> + template<input_range _Range1, input_range _Range2,
> + typename _Pred = ranges::equal_to,
> + typename _Proj1 = identity, typename _Proj2 =
> identity>
> + requires indirectly_comparable<iterator_t<_Range1>,
> iterator_t<_Range2>,
> + _Pred, _Proj1, _Proj2>
> + constexpr bool
> + operator()(_Range1&& __r1, _Range2&& __r2, _Pred __pred =
> {},
> + _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const
> + {
>
> Similar here:
> auto __first2 = ranges::begin(__r2);
> auto __last2 = ranges::end(__r2);
> if (__first2 == __last2)
> return true;
>
> And then move __first2 into the _S_impl call.
>
> + range_difference_t<_Range1> __n1 = -1;
> + range_difference_t<_Range1> __n2 = -1;
> + if constexpr (sized_range<_Range1>)
> + __n1 = ranges::size(__r1);
> + if constexpr (sized_range<_Range2>)
> + __n2 = ranges::size(__r2);
> + return _S_impl(ranges::begin(__r1), ranges::end(__r1),
> + ranges::begin(__r2), ranges::end(__r2),
> + std::move(__pred),
> + std::move(__proj1), std::move(__proj2),
> + __n1, __n2);
> + }
> +
> + template<typename _Iter1, typename _Sent1, typename _Iter2,
> typename _Sent2,
> + typename _Pred,
> + typename _Proj1, typename _Proj2>
> + static constexpr bool
> + _S_impl(_Iter1 __first1, _Sent1 __last1,
>
> I think I would make this function private. The user should not look
> into wrappers,
> but it does need to be public.
> I have slight preference for ordering arguments in following manner:
> first1, last1, n1,
> first2, last2, n2,
> + _Iter2 __first2, _Sent2 __last2,
> + _Pred __pred,
> + _Proj1 __proj1, _Proj2 __proj2,
> + iter_difference_t<_Iter1> __n1,
> + iter_difference_t<_Iter2> __n2)
> + {
>
> + if (__n1 != -1 && __n2 != -1)
>
> Very subjective, but I would other ifs, to not nest:
> if (__first2 == __last)
> return true;
> else if (n1 == -1 || n2 == -2)
> mismatch;
> else if (n1 < n2)
> return false;
> else if constexpr (random_access_iterator<_Iter1>)
> equal(first, first + n2, ....)
> else
> equal with counted.
>
> + {
> + if (__n1 < __n2)
> + return false;
> + if constexpr (random_access_iterator<_Iter1>)
> + return ranges::equal(__first1, __first1 + __n2,
>
> I think you need to cast __n2 to iter_difference_t<Iter1> here explicitly,
> it must fit because it is smaller or equal to n1, but still there may not be
> a candidate.
> + std::move(__first2), __last2,
> + std::move(__pred),
> + std::move(__proj1),
> std::move(__proj2));
> + else
> + return
> ranges::equal(counted_iterator(std::move(__first1), __n2),
>
> Similar here, cast to iter_difference_t<Iter1>.
> + default_sentinel,
> + std::move(__first2), __last2,
> + std::move(__pred),
> + std::move(__proj1),
> std::move(__proj2));
> + }
> + else
> + return ranges::mismatch(std::move(__first1), __last1,
> + std::move(__first2), __last2,
> + std::move(__pred),
> + std::move(__proj1),
> std::move(__proj2)).in2 == __last2;
> + }
> + };
> +
> + inline constexpr __starts_with_fn starts_with{};
> +
> + struct __ends_with_fn
> + {
> + template<input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
> + input_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
> + typename _Pred = ranges::equal_to,
> + typename _Proj1 = identity, typename _Proj2 = identity>
> + requires (forward_iterator<_Iter1> || sized_sentinel_for<_Sent1,
> _Iter1>)
> + && (forward_iterator<_Iter2> || sized_sentinel_for<_Sent2,
> _Iter2>)
> + && indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
> + constexpr bool
> + operator()(_Iter1 __first1, _Sent1 __last1,
> + _Iter2 __first2, _Sent2 __last2, _Pred __pred = {},
> + _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const
> + {
> + iter_difference_t<_Iter1> __n1 = -1;
> + iter_difference_t<_Iter2> __n2 = -1;
> + if constexpr (sized_sentinel_for<_Sent1, _Iter1>)
> + __n1 = __last1 - __first1;
> + if constexpr (sized_sentinel_for<_Sent2, _Iter2>)
> + __n2 = __last2 - __first2;
> + return _S_impl(std::move(__first1), __last1,
> + std::move(__first2), __last2,
> + std::move(__pred),
> + std::move(__proj1), std::move(__proj2),
> + __n1, __n2);
> + }
> +
> + template<input_range _Range1, input_range _Range2,
> + typename _Pred = ranges::equal_to,
> + typename _Proj1 = identity, typename _Proj2 = identity>
> + requires (forward_range<_Range1> || sized_range<_Range1>)
> + && (forward_range<_Range2> || sized_range<_Range2>)
> + && indirectly_comparable<iterator_t<_Range1>,
> iterator_t<_Range2>,
> + _Pred, _Proj1, _Proj2>
> + constexpr bool
> + operator()(_Range1&& __r1, _Range2&& __r2, _Pred __pred = {},
> + _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const
> + {
> + range_difference_t<_Range1> __n1 = -1;
> + range_difference_t<_Range1> __n2 = -1;
> + if constexpr (sized_range<_Range1>)
> + __n1 = ranges::size(__r1);
> + if constexpr (sized_range<_Range2>)
> + __n2 = ranges::size(__r2);
> + return _S_impl(ranges::begin(__r1), ranges::end(__r1),
> + ranges::begin(__r2), ranges::end(__r2),
> + std::move(__pred),
> + std::move(__proj1), std::move(__proj2),
> + __n1, __n2);
> + }
> +
> + template<typename _Iter1, typename _Sent1,
> + typename _Iter2, typename _Sent2,
> + typename _Pred,
> + typename _Proj1, typename _Proj2>
> + static constexpr bool
> + _S_impl(_Iter1 __first1, _Sent1 __last1,
>
> Similar comments about the private, and other of arguments as for above.,
> + _Iter2 __first2, _Sent2 __last2,
> + _Pred __pred,
> + _Proj1 __proj1, _Proj2 __proj2,
> + iter_difference_t<_Iter1> __n1,
> + iter_difference_t<_Iter2> __n2)
> + {
> + if (__n2 == -1)
> + {
> + if constexpr (forward_iterator<_Iter2>)
> + __n2 = ranges::distance(__first2, __last2);
> + else
> + // Size is known and passed by the caller.
> + __builtin_unreachable();
> + }
> +
> + if (__n1 != -1)
> + {
> + if (__n1 < __n2)
> + return false;
> + if constexpr (random_access_iterator<_Iter1>
> + || !bidirectional_iterator<_Iter1>)
> + {
> + ranges::advance(__first1, __n1 - __n2);
>
> I think you need to cast n2 to iter_difference_t<_Iter1> here explicitly.
> + return ranges::equal(std::move(__first1), __last1,
> + std::move(__first2), __last2,
> + std::move(__pred),
> + std::move(__proj1),
> std::move(__proj2));
> + }
> + }
> +
> + if constexpr (bidirectional_iterator<_Iter1>)
>
> + {
> + iter_difference_t<_Iter2> __m = __n2;
> + _Iter1 __it1 = ranges::next(__first1, __last1);
>
> Could you add a comment, that ranges::advance(__it, -__n2, __first) cannot be
> used here,
> because __n2 may not fit into iter_difference<Iter1>?
> + while (__m != 0 && __it1 != __first1)
> + {
> + --__m;
> + --__it1;
> + }
> + if (__m != 0)
> + return false;
> + return ranges::equal(__it1, __last1,
> + std::move(__first2), __last2,
> + std::move(__pred),
> + std::move(__proj1),
> std::move(__proj2));
> + }
> + else if constexpr (forward_iterator<_Iter1>)
> + {
> + if (__first2 == __last2)
> + return true;
>
> Could you make this if first in the _S_impl, and similarly for starts_with,
> I think it will make it a lot easier to reason about it.
> +
> + _Iter1 __prev_first1;
> + __n1 = 0;
> + while (true)
> + {
> + iter_difference_t<_Iter2> __m = __n2;
> + _Iter1 __it1 = __first1;
> + while (__m != 0 && __it1 != __last1)
> + {
> + ++__n1;
> + --__m;
> + ++__it1;
> + }
>
>
> + if (__m != 0)
> + {
> + // __glibcxx_assert(__it1 == __last1);
> + if (__n1 < __n2)
> + return false;
> + ranges::advance(__prev_first1, __n2 - __m);
>
> Again we need to cast __n2 - __m to iter_difference_t<Iter1>.
> + __first1 = __prev_first1;
> + break;
> + }
> + __prev_first1 = __first1;
> + __first1 = __it1;
> + }
> + return ranges::equal(__first1, __last1,
> + std::move(__first2), __last2,
> + std::move(__pred),
> + std::move(__proj1),
> std::move(__proj2));
> + }
> + else
> + // Should have been handled by the __n1 != -1 case.
>
> Could you expand a comment here, adding something like:
> If _first_1 is input_iterot, it must be sized, so this was handled by _n != 1
> case
> + __builtin_unreachable();
> + }
> +
> + };
> +
> + inline constexpr __ends_with_fn ends_with{};
> +#endif // __glibcxx_ranges_starts_ends_with
> +
> struct __find_end_fn
> {
> template<forward_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
> diff --git a/libstdc++-v3/include/bits/version.def
> b/libstdc++-v3/include/bits/version.def
> index 6ca148f0488f..8db1967cc184 100644
> --- a/libstdc++-v3/include/bits/version.def
> +++ b/libstdc++-v3/include/bits/version.def
> @@ -1660,6 +1660,14 @@ ftms = {
> };
> };
>
> +ftms = {
> + name = ranges_starts_ends_with;
> + values = {
> + v = 202106;
> + cxxmin = 23;
> + };
> +};
> +
> ftms = {
> name = constexpr_bitset;
> values = {
> diff --git a/libstdc++-v3/include/bits/version.h
> b/libstdc++-v3/include/bits/version.h
> index 48a090c14a3d..3749528633f2 100644
> --- a/libstdc++-v3/include/bits/version.h
> +++ b/libstdc++-v3/include/bits/version.h
> @@ -1848,6 +1848,16 @@
> #endif /* !defined(__cpp_lib_ranges_find_last) &&
> defined(__glibcxx_want_ranges_find_last) */
> #undef __glibcxx_want_ranges_find_last
>
> +#if !defined(__cpp_lib_ranges_starts_ends_with)
> +# if (__cplusplus >= 202100L)
> +# define __glibcxx_ranges_starts_ends_with 202106L
> +# if defined(__glibcxx_want_all) ||
> defined(__glibcxx_want_ranges_starts_ends_with)
> +# define __cpp_lib_ranges_starts_ends_with 202106L
> +# endif
> +# endif
> +#endif /* !defined(__cpp_lib_ranges_starts_ends_with) &&
> defined(__glibcxx_want_ranges_starts_ends_with) */
> +#undef __glibcxx_want_ranges_starts_ends_with
> +
> #if !defined(__cpp_lib_constexpr_bitset)
> # if (__cplusplus >= 202100L) && _GLIBCXX_HOSTED &&
> (__cpp_constexpr_dynamic_alloc)
> # define __glibcxx_constexpr_bitset 202202L
> diff --git a/libstdc++-v3/include/std/algorithm
> b/libstdc++-v3/include/std/algorithm
> index 321a5e22d86b..1563cdf2b17c 100644
> --- a/libstdc++-v3/include/std/algorithm
> +++ b/libstdc++-v3/include/std/algorithm
> @@ -74,6 +74,7 @@
> #define __glibcxx_want_ranges_contains
> #define __glibcxx_want_ranges_find_last
> #define __glibcxx_want_ranges_fold
> +#define __glibcxx_want_ranges_starts_ends_with
> #define __glibcxx_want_robust_nonmodifying_seq_ops
> #define __glibcxx_want_sample
> #define __glibcxx_want_shift
> diff --git a/libstdc++-v3/src/c++23/std.cc.in
> b/libstdc++-v3/src/c++23/std.cc.in
> index 417c8a1a5626..2e4b3f75234f 100644
> --- a/libstdc++-v3/src/c++23/std.cc.in
> +++ b/libstdc++-v3/src/c++23/std.cc.in
> @@ -506,6 +506,10 @@ export namespace std
> using ranges::find_last;
> using ranges::find_last_if;
> using ranges::find_last_if_not;
> +#endif
> +#if __cpp_lib_ranges_starts_ends_with
> + using ranges::starts_with;
> + using ranges::ends_with;
> #endif
> }
> }
> diff --git a/libstdc++-v3/testsuite/25_algorithms/ends_with/1.cc
> b/libstdc++-v3/testsuite/25_algorithms/ends_with/1.cc
> new file mode 100644
> index 000000000000..e5714101aecc
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/25_algorithms/ends_with/1.cc
> @@ -0,0 +1,129 @@
> +// { dg-do run { target c++23 } }
> +
> +#include <algorithm>
> +
> +#include <testsuite_hooks.h>
> +#include <testsuite_iterators.h>
> +
> +namespace ranges = std::ranges;
> +
> +template<typename Range1, typename Range2>
> +void
> +test01()
> +{
> + int n[] = {1,2,3,4,5,6,7,8,9,10};
> +
> + Range1 haystack(n, n+10);
> + Range2 needle(n+7, n+10);
> + VERIFY( ranges::ends_with(haystack, needle) );
> +
> + haystack = Range1(n);
> + needle = Range2(n, n+10);
> + VERIFY( ranges::ends_with(haystack, needle) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+6, n+9);
> + VERIFY( !ranges::ends_with(haystack, needle) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+6, n+9);
> + VERIFY( ranges::ends_with(haystack, needle,
> + [](int n, int m) { return std::abs(n - m)
> <= 1; }) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+6, n+9);
> + VERIFY( ranges::ends_with(haystack, needle,
> + ranges::equal_to{},
> + [](int n) { return n - 1; }) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+6, n+9);
> + VERIFY( ranges::ends_with(haystack, needle,
> + ranges::equal_to{},
> + std::identity{},
> + [](int n) { return n + 1; }) );
> +
> + haystack = Range1(n, n+5);
> + needle = Range2(n, n+10);
> + VERIFY( !ranges::ends_with(haystack, needle) );
> +}
> +
> +template<typename Range1, typename Range2>
> +void
> +test02()
> +{
> + int n[] = {1,2,3,4,5,6,7,8,9,10};
> +
> + Range1 haystack(n, n+10);
> + Range2 needle(n+7, n+10);
> + VERIFY( ranges::ends_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end()) );
> +
> + haystack = Range1(n);
> + needle = Range2(n, n+10);
> + VERIFY( ranges::ends_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end()) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+6, n+9);
> + VERIFY( !ranges::ends_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end()) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+6, n+9);
> + VERIFY( ranges::ends_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end(),
> + [](int n, int m) { return std::abs(n - m)
> <= 1; }) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+6, n+9);
> + VERIFY( ranges::ends_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end(),
> + ranges::equal_to{},
> + [](int n) { return n - 1; }) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+6, n+9);
> + VERIFY( ranges::ends_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end(),
> + ranges::equal_to{},
> + std::identity{},
> + [](int n) { return n + 1; }) );
> +
> + haystack = Range1(n, n+5);
> + needle = Range2(n, n+10);
> + VERIFY( !ranges::ends_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end()) );
> +
> + haystack = Range1(n, n+5);
> + needle = Range2(n+10, n+10);
> + VERIFY( ranges::ends_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end()) );
> +}
>
> Could you add the usual test with a second range using __max_diff_t as
> difference type.
> +
> +int
> +main()
> +{
> + using namespace __gnu_test;
> + using forward = test_forward_range<int>;
> + using input_sized = test_input_sized_range<int>;
> + using input_sized_sent = test_sized_range_sized_sent<int,
> input_iterator_wrapper>;
> + using random_access = test_random_access_range<int>;
> + using random_access_sized = test_random_access_sized_range<int>;
> + using random_access_sized_sent = test_sized_range_sized_sent<int,
> random_access_iterator_wrapper>;
> +
> + test01<forward, forward>();
> + test01<random_access, random_access>();
> + test02<forward, forward>();
> + test02<random_access, random_access>();
> +
> + test01<input_sized, input_sized>();
> + test01<random_access_sized, random_access_sized>();
> + // test02<input_sized, input_sized>(); constraint violation
> + test02<random_access_sized, random_access_sized>();
> +
> + test01<input_sized_sent, input_sized_sent>();
> + test01<random_access_sized_sent, random_access_sized_sent>();
> + test02<input_sized_sent, input_sized_sent>();
> + test02<random_access_sized_sent, random_access_sized_sent>();
> +}
> diff --git a/libstdc++-v3/testsuite/25_algorithms/starts_with/1.cc
> b/libstdc++-v3/testsuite/25_algorithms/starts_with/1.cc
> new file mode 100644
> index 000000000000..805f31ea2b03
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/25_algorithms/starts_with/1.cc
> @@ -0,0 +1,128 @@
> +// { dg-do run { target c++23 } }
> +
> +#include <algorithm>
> +
> +#include <testsuite_hooks.h>
> +#include <testsuite_iterators.h>
> +
> +namespace ranges = std::ranges;
> +
> +template<typename Range1, typename Range2>
> +void
> +test01()
> +{
> + int n[] = {1,2,3,4,5,6,7,8,9,10};
> +
> + Range1 haystack(n, n+10);
> + Range2 needle(n, n+3);
> + VERIFY( ranges::starts_with(haystack, needle) );
> +
> + haystack = Range1(n);
> + needle = Range2(n, n+10);
> + VERIFY( ranges::starts_with(haystack, needle) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+1, n+4);
> + VERIFY( !ranges::starts_with(haystack, needle) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+1, n+4);
> + VERIFY( ranges::starts_with(haystack, needle,
> + [](int n, int m) { return std::abs(n - m)
> <= 1; }) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+1, n+4);
> + VERIFY( ranges::starts_with(haystack, needle,
> + ranges::equal_to{},
> + [](int n) { return n + 1; }) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+1, n+4);
> + VERIFY( ranges::starts_with(haystack, needle,
> + ranges::equal_to{},
> + std::identity{},
> + [](int n) { return n - 1; }) );
> +
> + haystack = Range1(n, n+5);
> + needle = Range2(n, n+10);
> + VERIFY( !ranges::starts_with(haystack, needle) );
> +
> + haystack = Range1(n, n+5);
> + needle = Range2(n+10, n+10);
> + VERIFY( ranges::starts_with(haystack, needle) );
> +}
> +
> +template<typename Range1, typename Range2>
> +void
> +test02()
> +{
> + int n[] = {1,2,3,4,5,6,7,8,9,10};
> +
> + Range1 haystack(n, n+10);
> + Range2 needle(n, n+3);
> + VERIFY( ranges::starts_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end()) );
> +
> + haystack = Range1(n);
> + needle = Range2(n, n+10);
> + VERIFY( ranges::starts_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end()) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+1, n+4);
> + VERIFY( !ranges::starts_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end()) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+1, n+4);
> + VERIFY( ranges::starts_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end(),
> + [](int n, int m) { return std::abs(n - m)
> <= 1; }) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+1, n+4);
> + VERIFY( ranges::starts_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end(),
> + ranges::equal_to{},
> + [](int n) { return n + 1; }) );
> +
> + haystack = Range1(n);
> + needle = Range2(n+1, n+4);
> + VERIFY( ranges::starts_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end(),
> + ranges::equal_to{},
> + std::identity{},
> + [](int n) { return n - 1; }) );
> +
> + haystack = Range1(n, n+5);
> + needle = Range2(n, n+10);
> + VERIFY( !ranges::starts_with(haystack.begin(), haystack.end(),
> + needle.begin(), needle.end()) );
> +}
> +
> +int
> +main()
> +{
> + using namespace __gnu_test;
> + using input = test_input_range<int>;
> + using input_sized = test_input_sized_range<int>;
> + using input_sized_sent = test_sized_range_sized_sent<int,
> input_iterator_wrapper>;
> + using random_access = test_random_access_range<int>;
> + using random_access_sized = test_random_access_sized_range<int>;
> + using random_access_sized_sent = test_sized_range_sized_sent<int,
> random_access_iterator_wrapper>;
> +
> + test01<input, input>();
> + test01<random_access, random_access>();
> + test02<input, input>();
> + test02<random_access, random_access>();
> +
> + test01<input_sized, input_sized>();
> + test01<random_access_sized, random_access_sized>();
> + test02<input_sized, input_sized>();
> + test02<random_access_sized, random_access_sized>();
> +
> + test01<input_sized_sent, input_sized_sent>();
> + test01<random_access_sized_sent, random_access_sized_sent>();
> + test02<input_sized_sent, input_sized_sent>();
> + test02<random_access_sized_sent, random_access_sized_sent>();
> +}
> --
> 2.49.0.608.gcb96e1697a
>
>
>
