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| Iterator invalidation | ||||
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| Deduction guides(C++17) | |||||||
value_compare value_comp()const; | (constexpr since C++26) | |
Returns a function object that compares objects of typevalue_type (key-value pairs) by usingkey_comp() to compare the first components of the pairs.
Contents |
The value comparison function object.
Constant.
#include <iostream>#include <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::multimap<int,char, ModCmp> cont; cont={{1,'a'},{2,'b'},{3,'c'},{4,'d'},{5,'e'}}; auto comp_func= cont.value_comp(); for(conststd::pair<int,char> val={100,'a'};auto it: cont){constbool before= comp_func(it, val);constbool after= comp_func(val, it); std::cout<<'('<< it.first<<','<< it.second<<") ";if(!before&&!after)std::cout<<"equivalent to key ("<< val.first<<")\n";elseif(before)std::cout<<"goes before key ("<< val.first<<")\n";elseif(after)std::cout<<"goes after key ("<< val.first<<")\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 (public member function)[edit] |
