How to use the set::empty and set::clear STL functions in Visual C++

MORE INFORMATION

Required header

<set>

Prototype

template<class _K, class _Pr, class _A>
   class set {
   public:
   // Function 1:

      bool empty() const;

   // Function 2:
      void clear();
   }

Note The class/parameter names in the prototype may not match the version in the header file. Some have been modified to improve readability.

Description

The empty function returns true when there are no elements in the controlled sequence. By calling erase(begin,end), the clear function removes all elements in the controlled sequence. For more information about the erase function, please see set::erase.

Sample code

////////////////////////////////////////////////////////////////////// 
// 
// Compile options needed: -GX
// 
// SetEmpty&Clear.cpp:
//      Illustrates how to use the empty function to determine whether
//      there are elements in the controlled sequence. It also
//      illustrates how to use the clear function to remove all
//      elements from the controlled sequence.
// 
// Functions:
// 
//    empty        Returns true if there are no elements in the
//                 controlled sequence.
//    clear        Removes all elements from the controlled sequence.
// 
// Written by Derek Jamison
// of Microsoft Technical Support,
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
////////////////////////////////////////////////////////////////////// 

#pragma warning(disable:4786)
#include <set>
#include <iostream>

#if _MSC_VER > 1020   // if VC++ version is > 4.2
   using namespace std;  // std c++ libs implemented in std
   #endif

typedef set<int,less<int>,allocator<int> > SET_INT;

void truefalse(int x)
{
  cout << (x?"True":"False") << endl;
}

void main() {

  SET_INT s1;

  cout << "s1.empty() returned ";
  truefalse(s1.empty());  // True

  cout << "s1.insert(5)" << endl;
  s1.insert(5);
  cout << "s1.insert(8)" << endl;
  s1.insert(8);

  cout << "s1.empty() returned ";
  truefalse(s1.empty());  // False

  cout << "s1.clear()" << endl;
  s1.clear();

  cout << "s1.empty() returned ";
  truefalse(s1.empty());  // True
}

Program output

s1.empty() returned True
s1.insert(5)
s1.insert(8)
s1.empty() returned False
s1.clear()
s1.empty() returned True