std::multiset value_comp() method
- od C++98
// Const version only
value_compare value_comp() const;
Returns a function object that compares objects of type value_type
by comparing the first components of the pairs, same as key_comp()
.
Parameters
(none)
Return value
The value comparison function object.
Complexity
Constant - O(1).
Exceptions
(none)
Notes
Feature testing macro: __cpp_lib_generic_associative_lookup
(for overloads (3) and (4)).
Example
Main.cpp
#include <cassert>
#include <iostream>
#include <set>
// Example module 97 key compare function
struct ModCmp {
bool operator()(const int lhs, const int rhs) const
{
return (lhs % 97) < (rhs % 97);
}
};
int main()
{
std::multiset<int, ModCmp> cont{1, 2, 3, 4, 5};
// Same behaviour as key_comp()
auto comp_func = cont.value_comp();
const int val = 100;
for (int key : cont) {
bool before = comp_func(key, val);
bool after = comp_func(val, key);
if (!before && !after)
std::cout << key << " equivalent to key " << val << '\n';
else if (before)
std::cout << key << " goes before key " << val << '\n';
else if (after)
std::cout << key << " goes after key " << val << '\n';
else
assert(0); // Cannot happen
}
}
Possible output
1 goes before key 100
2 goes before key 100
3 equivalent to key 100
4 goes after key 100
5 goes after key 100
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