C++ Programming Code Examples
C++ > Visual C++ 5.0 Standard C++ Library Code Examples
Deque operatorlt - Returns true if d1 is lexicographically less than d2
Deque operatorlt - Returns true if d1 is lexicographically less than d2
operator<
Header
<deque>
template<class T, class A>
bool operator<(const deque<T, A>&d1, const deque<T, A>&d2) ;
Returns true if d1 is lexicographically less than d2, returns false otherwise.
The function returns the result of:
lexicographical_compare(d1.begin(), d1.end(), d2.begin())
The operator may be defined in terms of another operator. Basically, the two sequences are compared lexicographically . Lexicographical comparison is a dictionary-like comparison in which two words are compared for ordering. Assuming the sequences are represented by [first1, last1) and [first2, last2), the comparison works as follows: traverse the sequences comparing corresponding pair of elements e1 and e2:
* if e1 < e2, return true, else
* if e2 < e2, return false, otherwise
* continue to next corresponding pair of elements. If the first sequence gets exhausted, but the second is not, return true, otherwise return false.
Sample
#include <deque>
#include <iostream>
int main()
{
std::deque<int> c1, c2, c3, c4 ;
int i ;
for (i = 0; i < 10; i++)
{
c1.push_back(i) ;
c2.push_back(i*i) ;
c3.push_back(i*i*i) ;
c4.push_back(i) ;
}
if (c1 == c4)
std::cout << "c1 == c4" << std::endl ;
if (c2 != c3)
std::cout << "c2 != c3" << std::endl ;
if(c2 < c3)
std::cout << "c2 < c3" << std::endl ;
if(c3 > c2)
std::cout << "c3 > c2" << std::endl ;
c4.push_back(29) ;
if (c1 <= c4)
std::cout << "after c4.push_back(29), c1 <= c4" << std::endl ;
if (c3 >= c2)
std::cout << "c3 >= c2" << std::endl ;
std::swap(c3, c2) ;
std::cout << "after swapping c3 with c2, " ;
if (c3 >= c2)
std::cout << "c3 >= c2" << std::endl ;
else
std::cout << "c3 < c2" << std::endl ;
return 0 ;
}
Program Output
c1 == c4
c2 != c3
c2 < c3
c3 > c2
after c4.push_back(29), c1 <= c4
c3 >= c2
after swapping c3 with c2, c3 < c2
Return iterator to beginning. Returns an iterator pointing to the first element in the deque container. Notice that, unlike member deque::front, which returns a reference to the first element, this function returns a random access iterator pointing to it. If the container is empty, the returned iterator value shall not be dereferenced. deque::begin() is an inbuilt function in C++ STL which is declared in header file. deque::begin() returns an iterator which is referencing to the first element of the deque container associated with the function. Both begin() and end() are used to iterate through the deque container. This function does not accept any parameter.
Return iterator to end. Returns an iterator referring to the past-the-end element in the deque container. The past-the-end element is the theoretical element that would follow the last element in the deque container. It does not point to any element, and thus shall not be dereferenced. Because the ranges used by functions of the standard library do not include the element pointed by their closing iterator, this function is often used in combination with deque::begin to specify a range including all the elements in the container. If the container is empty, this function returns the same as deque::begin. deque::end() is an inbuilt function in C++ STL which is declared in<deque> header file. deque::end() returns an iterator which is referencing next to the last element of the deque container associated with the function. Both begin() and end() are used to iterate through the deque container.
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Lexicographical less-than comparison. Returns true if the range [first1,last1) compares lexicographically less than the range [first2,last2). The C++ function std::algorithm::lexicographical_compare() tests whether one range is lexicographically less than another or not. A lexicographical comparison is the kind of comparison generally used to sort words alphabetically in dictionaries. A lexicographical comparison is the kind of comparison generally used to sort words alphabetically in dictionaries; It involves comparing sequentially the elements that have the same position in both ranges against each other until one element is not equivalent to the other. The result of comparing these first non-matching elements is the result of the lexicographical comparison. If both sequences compare equal until one of them ends, the shorter sequence is lexicographically less than the longer one.
Add element at the end. Adds a new element at the end of the deque container, after its current last element. The content of val is copied (or moved) to the new element. This effectively increases the container size by one. push_back() function is used to push elements into a deque from the back. The new value is inserted into the deque at the end, before the current last element and the container size is increased by 1. This function does not return any value.
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Swap content. Exchanges the content of the container by the content of x, which is another deque object containing elements of the same type. Sizes may differ. After the call to this member function, the elements in this container are those which were in x before the call, and the elements of x are those which were in this. All iterators, references and pointers remain valid for the swapped objects. Notice that a non-member function exists with the same name, swap, overloading that algorithm with an optimization that behaves like this member function. This function does not return any value.
Relational operators for deque. Performs the appropriate comparison operation between the deque containers lhs and rhs. The equality comparison (operator==) is performed by first comparing sizes, and if they match, the elements are compared sequentially using operator==, stopping at the first mismatch (as if using algorithm equal). The less-than comparison (operator<) behaves as if using algorithm lexicographical_compare, which compares the elements sequentially using operator< in a reciprocal manner (i.e., checking both a<b and b<a) and stopping at the first occurrence. Function returns true if the condition holds, and false otherwise.
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