Why does lexical_cast make a copy?

From: Daniel T. (daniel_t_at_[hidden])
Date: 2002-03-22 10:26:45

I noticed that the function declaration of lexical_cast is:

     template<typename Target, typename Source>
Target lexical_cast(Source arg)

Namely that arg is a copy of the original source. Is there a specific 
reason that a copy is made? Why isn't it a 'const Source&' instead?

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