std::map::value_compare value_comp() const; |
Returns a function object that compares objects of type std::map::value_type (key-value pairs) by using key_comp
to compare the first components of the pairs.
(none).
The value comparison function object.
Constant.
#include <cassert> #include <iostream> #include <map> // 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::map<int, char, ModCmp> cont; cont = { { 1, 'a' }, { 2, 'b' }, { 3, 'c' }, { 4, 'd' }, { 5, 'e' } }; auto comp_func = cont.value_comp(); const std::pair<int, char> val = { 100, 'a' }; for (auto it : cont) { bool before = comp_func(it, val); bool after = comp_func(val, it); std::cout << '(' << it.first << ',' << it.second; if (!before && !after) std::cout << ") equivalent to key " << val.first << '\n'; else if (before) std::cout << ") goes before key " << val.first << '\n'; else if (after) std::cout << ") goes after key " << val.first << '\n'; else assert(0); // Cannot happen } }
Output:
returns the function that compares keys (public member function) |
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