WebJul 10, 2012 · Using a std::tuple as key for std::unordered_map. With the code below, I get a very confusing error in MSVC that seems to suggest the key type (an std::tuple) is … WebJun 15, 2024 · std::unordered_map is an implementation of hash table data structure, so it will arrange the elements internally according to the hash value using by std::unordered_map. But in case std::map it is usually a red black binary tree implementation. See the ref. from What will be order of key in unordered_map in c++ …
How to implement a map with three keys in C++ STL?
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WebDec 29, 2013 · And finally, as Benjamin Lindley answer already addresses, you need to use std::make_tuple: // d is data m [std::make_tuple (1, 'a', 'b')] = d; auto itr = m.find … WebApr 4, 2015 · 4 Answers. Your GUIDComparer is comparing for equality. The functor you pass to a map must generate weak ordering - i.e. it must compare less or compare greater, not equal. struct GUIDComparer { bool operator () (const GUID & Left, const GUID & Right) const { // comparison logic goes here return memcmp (&Left , &Right,sizeof (Right)) < 0; } }; WebMember type key_type is the type of the keys for the elements stored in the container, defined in map as an alias of its first template parameter (Key). If an rvalue (second version), the key is moved instead of copied when a new element is inserted. Return value A reference to the mapped value of the element with a key value equivalent to k. how does a recliner chair mechanism work