istream& problem
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From: James Dennett on 16 Sep 2006 16:49 Mike Wahler wrote: > "James Dennett" <jdennett(a)acm.org> wrote in message > news:WfSOg.4423$8J2.4070(a)fed1read11... >> c19h28o2 wrote: >>> Hi, >>> >>> can anyone tell me what i'm doing wrong here... >>> >>> #include <iostream> >>> #include <vector> >>> #include <string> >>> #include <sstream> >>> >>> using std::cout; >>> using std::cin; >>> using std::vector; >>> using std::string; >>> using std::stringstream; >>> >>> istream& isNumeric(istream& in); >>> >>> int main() >>> { >>> ..... >>> >>> on the istream& isNumer.... line I get the following error... >>> >>> error: expected constructor, destructor, or type conversion before '&' >>> token >>> >>> Thanks >>> >>> Michael >> You should write std::istream, or add a using declaration >> "using std::istream;". The compiler doesn't know what you >> mean by a plain (unqualified) "istream". > > Also, note that 'std::istream' is declared by <istream>, > which was not #included. It's defined by <istream>, but must of necessity be declared in <iostream> > Most compilers will have already > exposed 'std::istream' when <iostream> was #included, but > this is not guaranteed by the language standard. A definition is often included by <iostream>, but as you say, it's not required (only a declaration is required). > #include <istream> > using std::istream; > > istream& isNumeric(istream& in); While this only needs a declaration, its implementation almost certainly needs a definition of std::istream, which formally requires #include <istream>. -- James |