Question

这个简单的测试似乎与MSVC2015编译器有问题，但我不确定为什么

    #include <boost\container\flat_map.hpp>

TEST_METHOD(TestMap) {
    // Map declaration
    boost::container::flat_map<std::string, float> map2;
    // This works
    map2.insert(std::make_pair<std::string, float>("foo", 1.0F));
    // This errors
    map2.insert(std::make_pair("foo", 1.0F));
    // This (my preferred solution) also errors with same error as previous line
    map2.insert({"foo", 1.0F});
    // This works fine but is less efficient so I don't want to do this
    map2["foo"] = 1.0F;
}

错误是

unittest1.cpp(54): error C2668: 'boost::container::flat_map<std::string,float,std::less<Key>,boost::container::new_allocator<std::pair<std::string,float>>>::insert': ambiguous call to overloaded function
1>          with
1>          [
1>              Key=std::string
1>          ]
1>  h:\users\mushfaque.cradle\documents\cpp\include\boost\container\flat_map.hpp(847): note: could be 'void boost::container::flat_map<std::string,float,std::less<Key>,boost::container::new_allocator<std::pair<std::string,float>>>::insert(std::initializer_list<std::pair<std::string,float>>)'
1>          with
1>          [
1>              Key=std::string
1>          ]
1>  h:\users\mushfaque.cradle\documents\cpp\include\boost\container\flat_map.hpp(752): note: or       'std::pair<boost::container::container_detail::vec_iterator<Pointer,false>,bool> boost::container::flat_map<std::string,float,std::less<Key>,boost::container::new_allocator<std::pair<std::string,float>>>::insert(boost::container::container_detail::pair<Key,T> &&)'
1>          with
1>          [
1>              Pointer=std::pair<std::string,float> *,
1>              Key=std::string,
1>              T=float
1>          ]
1>  h:\users\mushfaque.cradle\documents\cpp\include\boost\container\flat_map.hpp(737): note: or       'std::pair<boost::container::container_detail::vec_iterator<Pointer,false>,bool> boost::container::flat_map<std::string,float,std::less<Key>,boost::container::new_allocator<std::pair<std::string,float>>>::insert(std::pair<std::string,float> &&)'
1>          with
1>          [
1>              Pointer=std::pair<std::string,float> *,
1>              Key=std::string
1>          ]
1>  h:\users\mushfaque.cradle\documents\cpp\include\boost\container\flat_map.hpp(722): note: or       'std::pair<boost::container::container_detail::vec_iterator<Pointer,false>,bool> boost::container::flat_map<std::string,float,std::less<Key>,boost::container::new_allocator<std::pair<std::string,float>>>::insert(const std::pair<std::string,float> &)'
1>          with
1>          [
1>              Pointer=std::pair<std::string,float> *,
1>              Key=std::string
1>          ]

我不明白为什么类型演绎不起作用，我必须每次都明确说明。

Answer 1

问题是make_pair("Foo", 1.0f)会返回std::pair<const char*, float>，std::pair<std::string, float>不是flat_map，而是可以转换为。{/ p> 同时，

insert＆＃39; movable_value_type&&有movable_value_type的非标准额外重载，其中boost::container::container_detail::pair<std::string, float>是std::pair<const char*, float>，显然，它也可以用// create a new taxonomy register_taxonomy( 'Category', 'projects', array( 'labels' => array( //'supports' => array( 'title', 'editor', 'comments', 'excerpt', 'custom-fields', 'thumbnail' ), 'name' => __('Skills'), 'singular_name' => __('skills'), 'edit_item' => __('Edit Skill'), 'update_item' => __('Update Skill'), 'new_item_name' => __('New Skill Name'), 'all_items' => __('All Skill Name'), 'add_new_item' => __('Add New Skill'), 'search_items' => __('Seacrh Skill Name'), 'popular_items' => __('Popular Skill'), 'separate_items_with_comments' => __('Separate Items With Comments'), 'add_or_remove_items' => __('Add Or Remove Items'), 'choose_from_most_used' => __('Choose From Most Used'), ), 'public' => TRUE, 'rewrite' => array( 'slug' => 'skills', 'with_front' => TRUE ), 'hierarchical' => TRUE, ) );构建。

所有用户定义的转换都同样好，编译器不知道要选哪一个，所以它会抱怨。

出于某种原因，使用std :: make_pair需要使用boost :: flat_map的显式类型

1 个答案: