C++ question

[Angus Leeming]

André, as our resident c++ guru, why does this compile:
        string data = ...;
        istringstream datastream(data);
        LyXLex lex(0,0);
        lex.setStream(datastream);

and this not:
        LyXLex lex(0,0);
        lex.setStream(istringstream(data));

The compiler complains that it is expecting a std::istream & and got a 
std::stringstream. Is it an lvalue thing? (passed & not const & so I guess 
that the stream is modified...)

-- 
Angus