Boost :: variant与无序映射

Question

有人可以告诉我，我如何获得boost :: Variant处理无序地图？

typedef boost::variant<long, string, double> lut_value;

unordered_map<lut_value, short> table;

我认为有一个用于boost :: variant的哈希函数，对吗？

编译器说：

./src/lookup/HashMap.o：在函数`std :: __ detail :: _ Hash_code_base中，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_ ，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail： ：variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_， boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_>，std :: pair，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_> const，short>，std :: _ Select1st，std :: allocator>，double，boost :: detail :: variant :: void_， boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_> const，short>>，std :: equal_to，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_ ，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail： ：variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_， boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_>>，std :: hash，std :: allocator>，double，boost： ：detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost ::detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_>>，std :: __ detail :: _ Mod_range_hashing， std :: __ detail :: __ Default_ranged_hash，false> :: _ M_hash_code（boost :: variant，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_> const＆）const'：
/usr/include/c++/4.6/bits/hashtable_policy.h:753：对`std :: hash，std :: allocator>的未定义引用，双精度，boost :: detail :: variant :: void_，boost :: detail： ：variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_， boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_>> :: operator（）（boost :: variant，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant ::void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_ ，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_>）const'
./src/lookup/HashMap.o：在函数`std :: __ detail :: _ Hash_code_base中，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_ ，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail： ：variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_， boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_>，std :: pair，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_> const，short>，std :: _ Select1st，std :: allocator>，double，boost :: detail :: variant :: void_， boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_> const，short>>，std :: equal_to，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_ ，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail： ：variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_， boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_>>，std :: hash，std :: allocator>，double，boost： ：detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost ::detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_>>，std :: __ detail :: _ Mod_range_hashing， std :: __ detail :: _ Default_ranged_hash，false> :: _ M_bucket_index（std :: __ detail :: _ Hash_node，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_> const，short>，false> const *，unsigned long）const'：
/usr/include/c++/4.6/bits/hashtable_policy.h:763：对`std :: hash，std :: allocator>的未定义引用，双精度，boost :: detail :: variant :: void_，boost :: detail： ：variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_， boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail ::变种::: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_>> :: operator（）（boost :: variant，std :: allocator>，double，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant ::void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_ ，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_，boost :: detail :: variant :: void_>）const'

Answer 1

是的，它需要一个哈希函数。你可以做：

#include <boost/functional/hash.hpp>
#include <boost/variant.hpp>

typedef boost::variant<long, std::string, double> lut_value;
std::unordered_map<lut_value, short, boost::hash<lut_value>> table;