Microsoft KB Archive/158038

= How to use the stack::operator< STL function in Visual C++ =

Article ID: 158038

Article Last Modified on 7/13/2005

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APPLIES TO

 The Standard C++ Library, when used with:  Microsoft Visual C++ 4.2 Enterprise Edition

 Microsoft Visual C++ 5.0 Enterprise Edition

 Microsoft Visual C++ 6.0 Enterprise Edition

 Microsoft Visual C++ 4.2 Professional Edition</li></ul>

 Microsoft Visual C++ 5.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Professional Edition</li></ul>

 Microsoft Visual C++ 6.0 Standard Edition</li></ul> </li></ul>

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This article was previously published under Q158038

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

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Prototype
template<class _TYPE, class _C, class _A> bool stack::operator<(const stack<_TYPE, _C, _A>& _X) const; 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 stack::operator< function returns true if the stack on the left side of the operator is less than the stack on the right side. The following steps are used to determine if one stack is less than another stack:
 * 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. //////////////////////////////////////////////////////////////////////


 * 1) pragma warning(disable:4786)

using namespace std;
 * 1) include
 * 2) include

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

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

allocator > 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;

} Program Output is: 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

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