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(C++26) | ||||
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| Associative | ||||
| Unordered associative | ||||
(C++11) | ||||
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| Iterator invalidation | ||||
| Member function table | ||||
| Non-member function table |
key_compare key_comp()const; | (since C++23) (constexpr since C++26) | |
Returns the function object that compares the keys, which is a copy of the key comparison object used by*this.
Contents |
The key comparison function object.
Constant.
#include <iostream>#include <flat_map>#include <utility> // Example module 97 key compare functionstruct ModCmp{bool operator()(int lhs,int rhs)const{return(lhs%97)<(rhs%97);}}; int main(){std::flat_map<int,char, ModCmp> cont; cont={{1,'a'},{2,'b'},{3,'c'},{4,'d'},{5,'e'}}; auto comp_func= cont.key_comp(); for(constauto it: cont){constbool before= comp_func(it.first,100);constbool after= comp_func(100, it.first); std::cout<<"Key ("<< it.first<<','<< it.second<<") ";if(!before&&!after)std::cout<<"equivalent to key (100)\n";elseif(before)std::cout<<"goes before key (100)\n";elseif(after)std::cout<<"goes after key (100)\n";elsestd::unreachable();}}
Output:
(1,a) goes before key (100)(2,b) goes before key (100)(3,c) equivalent to key (100)(4,d) goes after key (100)(5,e) goes after key (100)
returns the function that compares keys in objects of typevalue_type(public member function)[edit] |
