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std::experi...nges::equal(3)   C++ Standard Libary  std::experi...nges::equal(3)

NAME
     std::experimental::ranges::equal - std::experimental::ranges::equal

Synopsis
	Defined in header <experimental/ranges/algorithm>
	template< InputIterator I1, Sentinel<I1> S1, InputIterator I2,
	Sentinel<I2> S2,

		  class Pred = ranges::equal_to<>,
		  class Proj1 = ranges::identity, class Proj2 =
	ranges::identity  >						     (1)
     (ranges TS)
	    requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2>
	bool equal( I1 first1, S1 last1, I2 first2, S2 last2, Pred pred =
	Pred{},

		    Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{} );
	template< InputRange R1, InputRange R2, class Pred =
	ranges::equal_to<>,

		  class Proj1 = ranges::identity, class Proj2 =
	ranges::identity >
	    requires IndirectlyComparable<ranges::iterator_t<R1>,	     (2)
     (ranges TS)
	ranges::iterator_t<R2>,
					  Pred, Proj1, Proj2>
	bool equal( R1&& r1, R2&& r2, Pred pred = Pred{},

		    Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{} );
	template< InputIterator I1, Sentinel<I1> S1, class I2,

		  class Pred = ranges::equal_to<>,
		  class Proj1 = ranges::identity, class Proj2 =
	ranges::identity						       >
     (ranges TS)
	    requires InputIterator<std::decay_t<I2>> && !Range<I2> &&	     (3)
     (deprecated)
		     IndirectlyComparable<I1, std::decay_t<I2>, Pred,
	Proj1, Proj2>
	bool equal( I1 first1, S1 last1, I2&& first2_, Pred pred = Pred{},

		    Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{} );
	template< InputRange R1, class I2, class Pred = ranges::equal_to<>,

		  class Proj1 = ranges::identity, class Proj2 =
	ranges::identity >
	    requires  InputIterator<std::decay_t<I2>> && !Range<I2> &&	     (4)
     (ranges TS)
		     IndirectlyComparable<ranges::iterator_t<R1>,
     (deprecated)
	std::decay_t<I2>, Pred, Proj1, Proj2>
	bool equal( R1&& r1, I2&& first2_, Pred pred = Pred{},

		    Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{} );

	1) Returns true if the range [first1,  last1)  is  equal  to  the  range
     [first2, last2),
	and false otherwise.
	2) Same as (1), but uses r1 as the first source range and r2 as the sec-
     ond source
	range,	as  if	using  ranges::begin(r1)  as  first1, ranges::end(r1) as
     last1,
	ranges::begin(r2) as first2, and ranges::end(r2) as last2.
	3) Same as (1), except that the second range is considered to  end  when
     either the
	first  range  is exhausted or the first mismatch is detected. Equivalent
     to return
	last1  ==  ranges::mismatch(first1,  last1,   std::forward<I2>(first2_),
     comp, proj1,
	proj2).in1();
	4)  Same  as  (3),  but  uses  r1 as the first source range, as if using
     ranges::begin(r1)
	as first1 and ranges::end(r1) as last1.

	Two ranges are considered equal if they have the same number of elements
     and, for
	every iterator i in the range [first1, last1), ranges::invoke(pred,
	ranges::invoke(proj1,  *i),  ranges::invoke(proj2,  *(first2  +   (i   -
     first1)))) is true.

	Notwithstanding  the  declarations depicted above, the actual number and
     order of
	template parameters for algorithm declarations is unspecified. Thus,  if
     explicit
	template  arguments  are  used when calling an algorithm, the program is
     probably
	non-portable.

Parameters
	first1, last1 - the first range of the elements
	r1	      - the first range of the elements
	first2, last2 - the second range of the elements
	r2	      - the second range of the elements
	first2_       - the beginning of the second range of the elements
	pred	      - predicate to apply to the projected elements
	proj1	      - projection to apply to the elements in the first range
	proj2	      - projection to apply to the elements in the second range

Return value
	true if the two ranges are equal, otherwise returns false.

Notes
	ranges::equal should not be used to compare the ranges formed by the it-
     erators from
	std::unordered_set, std::unordered_multiset, std::unordered_map, or
	std::unordered_multimap because the order  in  which  the  elements  are
     stored in those
	containers  may  be  different even if the two containers store the same
     elements.

	When comparing entire containers for equality, operator== for the corre-
     sponding
	container are usually preferred.

Complexity
	1,2) If SizedSentinel<S1, I1> && SizedSentinel<S2, I2> is satisfied  and
     last1 -
	first1	!=  last2 - first2, no applications of the predicate and projec-
     tions.
	Otherwise, at most min(last1 - first1, last2 - first2)	applications  of
     the predicate
	and each projection.
	3,4)  At most last1 - first1 applications of the predicate and each pro-
     jection.

Possible implementation
	namespace detail
	{
	    template<InputIterator I1, SizedSentinel<I1> S1,
		     InputIterator I2, SizedSentinel<I1> S2>
	    bool check_size(I1& first1, S1& last1, I2& first2, S2& last2)
	    {
		return last1 - first1 != last2 - first2;
	    }

	    template<InputIterator I1, Sentinel<I1> S1, InputIterator  I2,  Sen-
     tinel<I1> S2>
	    bool check_size(I1& first1, S1& last1, I2& first2, S2& last2)
	    {
		return false;
	    }
	}

	template<InputIterator	I1,  Sentinel<I1>  S1,	InputIterator  I2,  Sen-
     tinel<I2> S2,
		 class Pred = ranges::equal_to<>,
		 class Proj1 = ranges::identity, class Proj2 = ranges::identity>
	    requires IndirectlyComparable<I1, I2, Pred, Proj1, Proj2>
	bool equal(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = Pred{},
		   Proj1 proj1 = Proj1{}, Proj2 proj2 = Proj2{})
	{
	    if (detail::check_size(first1, last1, first2, last2))
		return false;
	    for (;  first1  !=	last1  &&  first2  !=  last2;  (void)  ++first1,
     (void)++first2)
		if (!ranges::invoke(pred, ranges::invoke(proj1, *first1),
					  ranges::invoke(proj2, *first2)))
		    return false;
	    return first1 == last1 && first2 == last2;
	}

Example
	 This section is incomplete
	 Reason: no example

See also
	equal			determines if two sets of elements are the same
				(function template)
	find			finds the first element satisfying specific cri-
     teria
	find_if 		(function template)
	find_if_not
				returns  true  if one range is lexicographically
     less than
	lexicographical_compare another
				(function template)
	mismatch		finds the first position where two ranges differ
				(function template)
	search			searches for a range of elements
				(function template)

Category:
	  * Todo no example

http://cppreference.com 	   2024.06.10	    std::experi...nges::equal(3)
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