From: francis.glassborow@btinternet.com   
      
   On 14/02/2013 00:14, TS wrote:   
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   >   
   > I just noticed that C++0x includes unordered_map/set based on hash table.   
   > They allow users to specify their own hash and compare functions. However,   
   > it seems that they also include some default implementations of those   
   > functions, as compilers do not complain even if I don't provide them.   
   >   
   > My questions are   
   > 1. How are the performance of the default hash functions?   
   > 2. If I use a class defined by myself as a key, how does the default   
   > hash function know how to hash my type?   
   > 3. Have the default functions been optimized for certain built-in types?   
   > If so, what are they?   
      
   The answers to questions 1 & 3 are dependant on the implementation. As   
   for question 2, I think that all that is required is something that   
   works (e.g. it could simply hash on the raw bytes)   
      
   Francis   
      
      
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