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std::qsort(3)		       C++ Standard Libary		   std::qsort(3)

NAME
     std::qsort - std::qsort

Synopsis
	Defined in header <cstdlib>
	void qsort( void *ptr, std::size_t count,

		    std::size_t size, /* c-compare-pred */* comp );   (1)
	void qsort( void *ptr, std::size_t count,

		    std::size_t size, /* compare-pred */* comp );
	extern "C" using /* c-compare-pred */ = int(const void*,
	const void*);						      (2) (expo-
     sition only*)
	extern "C++" using /* compare-pred */ = int(const void*,
	const void*);

	Sorts  the  given  array pointed to by ptr in ascending order. The array
     contains count
	elements of size bytes. Function pointed to by comp is used  for  object
     comparison.

	If  comp  indicates  two elements as equivalent, their order is unspeci-
     fied.

	If the type of the elements of the array is not a
	PODType
	(until C++11)
	TriviallyCopyable type
	(since C++11), the behavior is undefined.

Parameters
	ptr   - pointer to the array to sort
	count - number of elements in the array
	size  - size of each element in the array in bytes
		comparison function which returns a negative  integer  value  if
     the first
		argument  is  less  than the second, a positive integer value if
     the first
		argument is greater than the second and zero  if  the  arguments
     are
		equivalent.

		The signature of the comparison function should be equivalent to
     the
		following:
	comp  -
		 int cmp(const void *a, const void *b);

		The  function  must not modify the objects passed to it and must
     return
		consistent results when called for the same objects,  regardless
     of their
		positions in the array.

Return value
	(none)

Notes
	Despite  the name, C++, C, and POSIX standards do not require this func-
     tion to be
	implemented using Quicksort or make any complexity or stability  guaran-
     tees.

	The  two overloads provided by the C++ standard library are distinct be-
     cause the
	types of the parameter comp are distinct (language linkage  is	part  of
     its type).

Example
	The following code sorts an array of integers using qsort():

     // Run this code

      #include <array>
      #include <climits>
      #include <compare>
      #include <cstdlib>
      #include <iostream>

      int main()
      {
	  std::array a{-2, 99, 0, -743, INT_MAX, 2, INT_MIN, 4};

	  std::qsort
	  (
	      a.data(),
	      a.size(),
	      sizeof(decltype(a)::value_type),
	      [](const void* x, const void* y)
	      {
		  const int arg1 = *static_cast<const int*>(x);
		  const int arg2 = *static_cast<const int*>(y);
		  const auto cmp = arg1 <=> arg2;
		  if (cmp < 0)
		      return -1;
		  if (cmp > 0)
		      return 1;
		  return 0;
	      }
	  );

	  for (int ai : a)
	      std::cout << ai << ' ';
	  std::cout << '\n';
      }

Output:
      -2147483648 -743 -2 0 2 4 99 2147483647

	Defect reports

	The  following	behavior-changing  defect  reports were applied retroac-
     tively to
	previously published C++ standards.

	  DR	Applied to	       Behavior as  published		    Cor-
     rect behavior
	LWG 405 C++98	   the elements of the array could have any type limited
     to PODType

See also
	bsearch    searches an array for an element of unspecified type
		   (function)
	sort	   sorts a range into ascending order
		   (function template)
	is_trivial checks if a type is trivial
	(C++11)    (class template)
	C documentation for
	qsort

http://cppreference.com 	   2024.06.10			   std::qsort(3)
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