gcc-3.0.2 + hash_map<string,int> compilation problems
Mon Apr 8 18:10:00 GMT 2002
On Mon, Apr 08, 2002 at 11:42:45PM +0200, Stefan Olsson wrote:
> I have had the same issue and solved it by declaring:
> #include <string>
> #include <ext/hash_map>
> namespace __gnu_cxx
> template<> struct hash< std::string >
> size_t operator()( const std::string& x ) const
> return hash< const char* >()( x.c_str() );
That's definitely one way to do it; if you look at ext/stl_hash_fun.h you'll
see what's happening here. You could return __stl_hash_string directly.
If you're going to use a nonportable extension, why stop with just one? :-)
> I guess that the reason for not having this declared in the std::string
> is that the hash* are extensions to the standard.
I'm assuming you meant /for/ std::string rather than /in/ std::string.
Take a look at the notes from authors of the hash* stuff:
> Maybe something like
> the above could be added into the codebase somewhere else?
As the second link points out, the default hashing function is only a guess.
You are encouraged to write your own and use it instead of __stl_hash_string.
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