C++ 声明 std::map 常量
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/4396808/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Declaring std::map constants
提问by Chandan Shetty SP
How to declare std map constants i.e.,
如何声明 std 映射常量，即
int a[10] = { 1, 2, 3 ,4 };
std::map <int, int> MapType[5] = { };
int main()
{
}
In the about snippet it is possible to give values 1,2,3,4 to integer array a, similarly how to declare some constant MapTypevalues instead of adding values inside main() function.
在 about 片段中，可以将值 1,2,3,4 赋予整数数组a，类似于如何声明一些常量MapType值而不是在 main() 函数中添加值。
回答by Matthew Flaschen
In C++0x, it will be:
在 C++0x 中，它将是：
map<int, int> m = {{1,2}, {3,4}};
回答by Tony Delroy
UPDATE: with C++11 onwards you can...
更新：从 C++11 开始，你可以......
std::map<int, int> my_map{ {1, 5}, {2, 15}, {-3, 17} };
...or similar, where each pair of values - e.g. {1, 5}- encodes a key - 1- and a mapped-to value - 5. The same works for unordered_map(a hash table version) too.
...或类似的，其中每对值 - 例如{1, 5}- 编码一个键 - 1- 和映射到的值 - 5。这同样适用于unordered_map（哈希表版本）。
Using just the C++03 Standard routines, consider:
仅使用 C++03 标准例程，请考虑：
#include <iostream>
#include <map>
typedef std::map<int, std::string> Map;
const Map::value_type x[] = { std::make_pair(3, "three"),
std::make_pair(6, "six"),
std::make_pair(-2, "minus two"),
std::make_pair(4, "four") };
const Map m(x, x + sizeof x / sizeof x[0]);
int main()
{
// print it out to show it works...
for (Map::const_iterator i = m.begin();
i != m.end(); ++i)
std::cout << i->first << " -> " << i->second << '\n';
}
回答by Kaz Dragon
I was so taken by the Boost.Assignsolution to this problem that I wrote a blog post about it about a year and a half ago (just before I gave up on blogging):
我被Boost.Assign解决这个问题的方法所吸引，以至于我在大约一年半前（就在我放弃博客之前）写了一篇关于它的博客文章：
The relevant code from the post was this:
帖子中的相关代码是这样的：
#include <boost/assign/list_of.hpp>
#include <map>
static std::map<int, int> amap = boost::assign::map_list_of
(0, 1)
(1, 1)
(2, 2)
(3, 3)
(4, 5)
(5, 8);
int f(int x)
{
return amap[x];
}
