I've asked in one of [my posts](https://stackoverflow.com/questions/6404079/alternative-to-boostlexical-cast) a question about alternative to `boost::lexical_cast` and amongst many replies I've got one suggestion `stoi` as a viable alternative.  

I've decided to test it and to my surprise as a second argument to this function (argument describing size) is a pointer to `size_t` type, not actual `size_t` type. Is there any logical explanation for that and in what way it is better to have a pointer to actual object than object itself (just in this particular case when size is concerned and I wouldn't instinctively assign size with pointer)?

Link to stoi doc: <http://msdn.microsoft.com/en-us/library/ee404860.aspx>