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Can I construct an std::map where the key type is a reference type, e.g. Foo & and if not, why not?
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We can use any of the data types as the data type of the key of the map. Even a user-defined data type can be used as key data type.
Yes -- when you insert an item into an std::map, you pass it by value, so what it contains is a copy of what you passed.
List: A list in STL is used to implement the doubly-linked lists. Unlike an array, lists are used to store the data, which is not contiguous.
According to C++ Standard 23.1.2/7 key_type should be assignable. Reference type is not.
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No, because many of the functions in std::map takes a reference to the keytype and references to references are illegal in C++.
/A.B.
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