请问.net 中的hash_map

[mmosquito]

我想使用一个
hash_map<string,int>
代码如下：
std::hash_map<std::string,int> myMap;
myMap["hello"] = 1;

but error:
c:\Program Files\Microsoft Visual Studio .NET\Vc7\include\xhash(38) : error C2440: “类型转换” : 无法从“const std::string”转换为“size_t”

请问如何实现？

[小笨和漂向北方]

为什么要把string作为key呢？好像这个key只能是int？

如果不是非要把string作为key，那么
std::hash_map<int，std::string> myMap;
myMap[1] ="hello";

[joachern]

up

[mmosquito]

只允许int作key,还叫什么模板?stl_port就可以
std::hash_map<std::string,int> myMap;
myMap["hello"] = 1;

[ahao]

.net2003上通过
没问题

[bm1408]

up!

[bm1408]

看了一下！

应该为：
std::hash_map<std::string,int> myMap;
myMap["hello"] = 1;

[qqchen79]

stl_port allows string to be used as the key of hash_set/hash_map because it provides a default implementation of Hash<string> (the hash functor specialized for string).

On the other hand, VC7 Stl doesn't provide such a functor. Thus you have to work out one on your own:

using namespace std;

class string_hash
{
public:
enum
{ // parameters for hash table
bucket_size = 4, // 0 < bucket_size
min_buckets = 8
}; // min_buckets = 2 ^^ N, 0 < N

string_hash() {}
size_t operator()(const string& key) const
{
long h = 0;
for(int i = 0; i < key.size(); ++ i) {
h += key[i];
}
return (size_t)h;
}

bool operator()(const string& key1, const string& key2) const
{
return (key1.compare(key2) < 0);
}
};

//this is just a simple implementation demonstrates what need to be done for a
//hash functor. It's not optimized.
....
hash_map<std::string, int, string_hash> myMap;
....

[nsly]

我觉得是现insert后，然后才可以赋值。乱说的，因为没有做过。

[magicblue]

qqchen79(知秋一叶 [MS MVP])

it seems too fragile. why MS insist on using P.J's stl rather than SGI?

i create a template class to implement serialization. when i compiling it, i get a dozen of errors in xdebug file that belong to P.J stl

[mmosquito]

谢谢qqchen79
没想到沉了这么久的帖子也有人看，再次感谢ms mvp
其实不久之后我也解决了这个问题，ms没有文档，其实看看源代码就好。