Proper and portable ways using manipulator

Proper and portable ways using manipulator

[Wei Qin]

Hi,
	I used some manipulators in the form of

#include <iostream>
#include <ios>

int main () {

	std::cout << std::showbase << std::hex << 100 << std::endl;
}

	This compiles fine with g++ 3.x. However, it fails on g++ 2.96
since it cannot find ios. When I remove ios, it cannot find showbase. Then
I change std::showbase to std::ios::showbase, but this showbase is not a
manipulator any more. As a result the program outputs 8064 instead of
0x64.
	So my question is: Is there any good coding practice to make sure
that the same code compiles for both and works as intended? Thanks.

Wei

Re: Proper and portable ways using manipulator

[LLeweLLyn Reese]

Wei Qin <wqin@EE.Princeton.EDU> writes:

> Hi,
> 	I used some manipulators in the form of
> 
> #include <iostream>
> #include <ios>

Try:
#include <iomanip>

instead. (Note: I don't have 2.96 availible to test.)

> 
> int main () {
> 
> 	std::cout << std::showbase << std::hex << 100 << std::endl;
> }
> 
> 	This compiles fine with g++ 3.x. However, it fails on g++ 2.96
> since it cannot find ios. When I remove ios, it cannot find showbase. Then
> I change std::showbase to std::ios::showbase, but this showbase is not a
> manipulator any more. As a result the program outputs 8064 instead of
> 0x64.
> 	So my question is: Is there any good coding practice to make sure
> that the same code compiles for both and works as intended? Thanks.

Compile every change with both compilers.

Re: Proper and portable ways using manipulator

[Wei Qin]

Hi, LLeweLLyn,

	Thanks for the reply.
	I tried <iomanip>, it works for g++3, but again not for g++2.
I grepped its g++-2 directory and the only showbase that I found is an enum.
So I now assume that there is no showbase manipulator in that library.

Is there any similar backward compatible way to use manipulators as
the hash_map one given at
http://gcc.gnu.org/onlinedocs/libstdc++/faq/#5_4
?

Wei

On 7 Aug 2003, LLeweLLyn Reese wrote:

> Wei Qin <wqin@EE.Princeton.EDU> writes:
>
> > Hi,
> > 	I used some manipulators in the form of
> >
> > #include <iostream>
> > #include <ios>
>
> Try:
> #include <iomanip>
>
> instead. (Note: I don't have 2.96 availible to test.)
>
> >
> > int main () {
> >
> > 	std::cout << std::showbase << std::hex << 100 << std::endl;
> > }
> >
> > 	This compiles fine with g++ 3.x. However, it fails on g++ 2.96
> > since it cannot find ios. When I remove ios, it cannot find showbase. Then
> > I change std::showbase to std::ios::showbase, but this showbase is not a
> > manipulator any more. As a result the program outputs 8064 instead of
> > 0x64.
> > 	So my question is: Is there any good coding practice to make sure
> > that the same code compiles for both and works as intended? Thanks.
>
> Compile every change with both compilers.
>

Re: Proper and portable ways using manipulator

[LLeweLLyn Reese]

Wei Qin <wqin@EE.Princeton.EDU> writes:

> Hi, LLeweLLyn,
> 
> 	Thanks for the reply.
> 	I tried <iomanip>, it works for g++3, but again not for g++2.
> I grepped its g++-2 directory and the only showbase that I found is an enum.
> So I now assume that there is no showbase manipulator in that
> 	library.

Probably correct.

> 
> Is there any similar backward compatible way to use manipulators as
> the hash_map one given at
> http://gcc.gnu.org/onlinedocs/libstdc++/faq/#5_4
> ?
[snip]

I don't know. I doubt it; there's backward/iostream.h , but it just
    #includes <iostream> and adds using declarations to bring
    appropriate things into the global namespaces. Same for the other
    iostream headers in backward/.