INFO: STL Sample for the stack::operation

• The Standard C++ Library, used with:
  • Microsoft Visual C++, 32-bit Editions, versions 4.2, 5.0, 6.0

SUMMARY

The sample code below illustrates how to use the stack::operator< STL function in Visual C++.

MORE INFORMATION

Required Header

   <stack> 

Prototype

   template<class _TYPE, class _C, class _A>
   bool stack::operator<(const stack<_TYPE, _C, _A>& _X) const; 

Description

1. Compare the bottom-most (very first element pushed onto the stack).



2. If the elements are different, the stack with the smaller element is less than the stack with the greater element. Go to Step 5.



3. If the elements are the same and there are more elements, move to the next element in the stack and go back to step 2.



4. If all the elements in the stacks are processed at this point, the stacks are equal.



5. Done.

Sample Code

////////////////////////////////////////////////////////////////////// 
// 
// Compile options needed: /GX
// 
// StackLessThan.cpp : Illustrates how to use the stack::operator<
//                     function to determine if one stack is less than
//                     another stack.
// 
// Functions:
// 
//    operator< :  Returns true if the stack is smaller than the stack
//                 passed as the operand.
// 
// Written by Derek Jamison
// of Microsoft Product Support Services,
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
////////////////////////////////////////////////////////////////////// 

#pragma warning(disable:4786)

#include <stack>
#include <iostream>

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

typedef stack<double, deque<double, allocator<double> >,

              allocator<double> > STACK_DOUBLE;

void main()

{

   STACK_DOUBLE stack1,stack2;

   // Add item 4.0 to Stack1. Stack1 contains 4.0.
   cout << "stack1.push(4.0)  s1=[4.0]" << endl;
   stack1.push(4.0);

   // Add item 3.0 to Stack1. Stack1 contains 3.0(top) and 4.0(bottom).
   cout << "stack1.push(3.0)  s1=[3.0 4.0]" << endl;
   stack1.push(3.0);

   // Add item 4.0 to Stack2. Stack2 contains 4.0 (top=bottom).
   cout << "stack2.push(4.0)  s2=[4.0]" << endl;
   stack2.push(4.0);

   // Compare if Stack1 is smaller than Stack2. Should return False.
   cout << "stack1<stack2 is " <<
      ((stack1<stack2)? "True": "False") << endl << endl;

   // Add item 6.0 to Stack2. Stack2 contains 6.0(top) and 4.0(bottom).
   cout << "stack2.push(6.0)  s2=[6.0 4.0]" << endl;
   stack2.push(6.0);

   // Compare if Stack1 is smaller than Stack2. Should return True.
   cout << "stack1<stack2 is " <<
      ((stack1<stack2)? "True": "False") << endl << endl;

   // Add item 8.0 to Stack2. Stack2 contains 8.0(top), 6.0 and
   // 4.0(bottom).
   cout << "stack2.push(8.0)  s2=[8.0 6.0 4.0]" << endl;
   stack2.push(8.0);

   // Compare if Stack1 is smaller than Stack2. Should return True.
   cout << "stack1<stack2 is " <<
      ((stack1,stack2)? "True": "False") << endl << endl;

   // Delete item 8.0 from Stack2.
   cout << "stack2.pop()      s2=[6.0 4.0]" << endl;
   stack2.pop();

   // Delete item 6.0 from Stack2.
   cout << "stack2.pop()      s2=[4.0]" << endl;
   stack2.pop();

   // Add item 3.0 to Stack2. Stack2 contains 3.0(top) and 4.0(bottom).
   cout << "stack2.push(3.0)  s2=[3.0 4.0]" << endl;
   stack2.push(3.0);

   // Compare if Stack1 is smaller than Stack2. Should return False.
   cout << "stack1<stack2 is " <<
      ((stack1<stack2)? "True": "False") << endl << endl;

   // Delete item 3.0 from Stack2.
   cout << "stack2.pop()      s2=[4.0]" << endl;
   stack2.pop();

   // Delete item 4.0 from Stack2.
   cout << "stack2.pop()      s2=[]" << endl;
   stack2.pop();

   // Add item 8.0 to Stack2. Stack2 contains 8.0(top=bottom).
   cout << "stack2.push(8.0)  s2=[8.0]" << endl;
   stack2.push(8.0);

   // Compare if Stack1 is smaller than Stack2. Should return True.
   cout << "stack1<stack2 is " <<
      ((stack1<stack2)? "True": "False") << endl << endl;

} 

stack1.push(4.0)  s1=[4.0]
stack1.push(3.0)  s1=[3.0 4.0]
stack2.push(4.0)  s2=[4.0]
stack1<stack2 is False

stack2.push(6.0)  s2=[6.0 4.0]
stack1<stack2 is True

stack2.push(8.0)  s2=[8.0 6.0 4.0]
stack1<stack2 is True
<BR/><BR/>
stack2.pop()      s2=[6.0 4.0]
stack2.pop()      s2=[4.0]
stack2.push(3.0)  s2=[3.0 4.0]
stack1<stack2 is False

stack2.pop()      s2=[4.0]
stack2.pop()      s2=[]
stack2.push(8.0)  s2=[8.0]
stack1<stack2 is True 

REFERENCES

Visual C++ Books On Line: Visual C++ Books:C/C++:Standard C++ Library Reference.

Additional query words: STL STLSample operator

Keywords : kbcode kbVC420 kbVC500 kbVC600 kbDSupport STLIss
Version : winnt:4.2,5.0,6.0
Platform : winnt
Issue type : kbinfo