| Defined in header <utility> | ||||
|---|---|---|---|---|
| (1) | (until C++14) | ||
| (1) | (since C++14) | ||
| (2) | (until C++14) | ||
| (2) | (since C++14) | ||
| (3) | (until C++14) | ||
| (3) | (since C++14) | ||
| (4) | (until C++14) | ||
| (4) | (since C++14) | ||
| (5) | (until C++14) | ||
| (5) | (since C++14) | ||
| (6) | (until C++14) | ||
| (6) | (since C++14) |
1-2) Tests if both elements of lhs and rhs are equal, that is, compares
lhs.first with rhs.first and lhs.second with rhs.second 3-6) Compares
lhs and rhs lexicographically, that is, compares the first elements and only if they are equivalent, compares the second elements.Parameters
| lhs, rhs | - | pairs to compare |
Return value
1) true if both lhs.first == rhs.first and lhs.second == rhs.second, otherwise false.
2) true if either lhs.first != rhs.first or lhs.second != rhs.second, otherwise false.
3) If lhs.first<rhs.first, returns true. Otherwise, if rhs.first<lhs.first, returns false. Otherwise, if lhs.second<rhs.second, returns true. Otherwise, returns false.
4) !(rhs < lhs).
5) rhs < lhs.
6) !(lhs < rhs).
Example
Because operator< is defined for pairs, containers of pairs can be sorted.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | #include <iostream>#include <utility>#include <vector>#include <algorithm>#include <string> int main(){ std::vector<std::pair<int, std::string>> v = { {2, "baz"}, {2, "bar"}, {1, "foo"} }; std::sort(v.begin(), v.end()); for(auto p: v) { std::cout << "(" << p.first << "," << p.second << ")\n"; }} |
Output:
1 2 3 | (1,foo)(2,bar)(2,baz) |
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