From: daniel.kruegler@googlemail.com   
      
   Am 15.10.2012 22:22, schrieb Daniel Krügler:   
   > Other implementations validate via an non-portable O(1) address   
   > test, whether the argument reference (assuming continuous container   
   > like std::vector) is part of the container.   
      
   Upon a second reflection I think this can be done portably given the   
   fact that std::less induces a total order and that all address values   
   within an array have a relative ordering equivalent to that of the   
   corresponding index values. Given this we can always detect whether   
   any other object pointer value is within or outside of the array.   
      
   It very rarely happens that the library provides so much stronger   
   guarantees about fundamental type properties, so that it is very easy   
   to forget that...   
      
   Greetings from Bremen,   
      
   Daniel Krügler   
      
      
      
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