[PATCH] libstdc++: Implement C++23 P1659R3 starts_with and ends_with
Tomasz Kaminski
tkaminsk@redhat.com
Mon May 19 13:21:31 GMT 2025
On Mon, May 19, 2025 at 9:59 AM Tomasz Kaminski <tkaminsk@redhat.com> wrote:
>
>
> On Mon, May 19, 2025 at 6:47 AM Patrick Palka <ppalka@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.
> + 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
>>
>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://gcc.gnu.org/pipermail/libstdc++/attachments/20250519/9dd16d12/attachment-0001.htm>
More information about the Libstdc++
mailing list