Iostream

[ncstate]

it seems when i try to compile this simple code I get an error message i
believe is from g++ not finding the IOSTREAM header file. i found the
header file in /usr/include/c++/3.2.2/ so that is why it is included
like that. suggestions?

I'm running red hat 9



code :



#include </usr/include/c++/3.2.2/iostream>



int main()



{

cout << endl << endl << "Jeff" << endl;

cout << "E115 Sec 010 B" << endl;

cout << "Hello World" << endl << endl << endl;



return 0;

}

errors:



project2.C: In function `int main()':

project2.C:6: `cout' undeclared (first use this function)

project2.C:6: (Each undeclared identifier is reported only once for each

function it appears

 

[Jonathan Mcdougall]

it seems when i try to compile this simple code I get an error

message i believe is from g++ not finding the IOSTREAM header file. i
found the header file in /usr/include/c++/3.2.2/ so that is why it is
included like that. suggestions?

I'm running red hat 9

#include </usr/include/c++/3.2.2/iostream>

I don't know about the requirements of the standard about that, but imho, if
your compiler forces you to specify such a path, it is broken. Ask in a
newsgroup supporting it

http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.9

int main()
{

cout << endl << endl << "Jeff" << endl;

errors:
project2.C: In function `int main()':

project2.C:6: `cout' undeclared (first use this function)

'cout' is defined in the std namespace (as all standard functions, classes
and objects are), so you must explictly refer to it :

std::cout << std::endl << "Jeff" << std::endl;

Or look up using directive and declaration.


Jonathan

 

[Victor Bazarov]

it seems when i try to compile this simple code I get an error message i
believe is from g++ not finding the IOSTREAM header file. i found the
header file in /usr/include/c++/3.2.2/ so that is why it is included
like that. suggestions?

I'm running red hat 9



code :



#include </usr/include/c++/3.2.2/iostream>



int main()



{

cout << endl << endl << "Jeff" << endl;

cout << "E115 Sec 010 B" << endl;

cout << "Hello World" << endl << endl << endl;



return 0;

}

errors:



project2.C: In function `int main()':

project2.C:6: `cout' undeclared (first use this function)

project2.C:6: (Each undeclared identifier is reported only once for each

function it appears

The 'cout' object is declared in the 'std' namespace. You should
either prefix it with "std::" or declare that you're using that
name:

using std::cout;
using std::endl; // as well

Get a decent book on C++.

Victor

 

[MPBroida]

it seems when i try to compile this simple code I get an error message i
believe is from g++ not finding the IOSTREAM header file. i found the
header file in /usr/include/c++/3.2.2/ so that is why it is included
like that. suggestions?

I'm running red hat 9

code :

#include </usr/include/c++/3.2.2/iostream>

It's been a little while, but I seem to recall that
including a file from the "builtin" include dirs is
done via:
#include <filename>
That tells the compiler to use its own include path(s).

But including a USER file is done via:
#include "filename"
That tells the compiler to use the include paths from
the compile commandline (or defaults)(or project/etc).

Try changing the < and > to " and " and see what
happens.

Mike

 

[David Rubin]

ncstate wrote:
[snip - rearranged]

#include </usr/include/c++/3.2.2/iostream>

int main()
{
cout << endl << endl << "Jeff" << endl; [snip]
project2.C: In function `int main()':
project2.C:6: `cout' undeclared (first use this function)
project2.C:6: (Each undeclared identifier is reported only once for each
function it appears

Try std::cout and std::endl or 'using namespace std;' I found this
diagnostic a bit confusing too the first time I saw it.

/david

 

[Mike Wahler]

it seems when i try to compile this simple code I get an error message i
believe is from g++ not finding the IOSTREAM header file.

No, it's telling you it cannot find the declaration of
an identifier you've used ('cout').

i found the
header file in /usr/include/c++/3.2.2/ so that is why it is included
like that. suggestions?

Don't include it 'like that'.

I'm running red hat 9

This doesn't matter. C++ is a platform independent language.

code :

#include </usr/include/c++/3.2.2/iostream>

Change to:

#include <iostream>

If this does not work, then your compiler is installed
and/or configured incorrectly.

Note that from the language's perspective <iostream> is a
standard *header* name, it does *not* signify a "file" name.
Many if not most implementations do provide an actual file
with the same or a similar name to implement a standard header,
but this is an implementation detail, not specified or
required by the language. E.g. a compiler could provide the
required declarations as 'hard coded' if it wanted and would
still be conforming -- the #include statement would still be
required however).

[Gratuitous whitespace removed from code below]

int main()
{
cout << endl << endl << "Jeff" << endl;
cout << "E115 Sec 010 B" << endl;
cout << "Hello World" << endl << endl << endl;

return 0;
}

errors:

project2.C: In function `int main()':

project2.C:6: `cout' undeclared (first use this function)

This is because 'cout' (and all standard library identifiers
except macros are declared in namespace 'std').

project2.C:6: (Each undeclared identifier is reported only once for each

function it appears

#include <iostream>

int main()
{
std::cout << "Hello world\n";
return 0;
}


or


#include <iostream>

using std::cout;

int main()
{
cout << "Hello world\n";
return 0;
}


or


#include <iostream>

using namespace std;

int main()
{
cout << "Hello world\n";
return 0;
}

(If desired, the scope of 'cout' can be further restricted
by putting the 'using' directive or declaration inside the
'main()' function.)

Note: while most implementations will work without it,
the declaration for 'endl' is provided by <ostream>.
It is allowed to be, but not required to be, provided by
<iostream>. 'endl' is also in namespace 'std'. (Its
'full name' is 'std::endl')

BTW, which C++ book(s) are you reading?

-Mike

 

[Mike Wahler]

Try std::cout and std::endl or 'using namespace std;'

or:
using std::cout;
using std::endl;

I found this
diagnostic a bit confusing too the first time I saw it.

"'cout' undeclared." Exactly the case. How much more specific
could it be?

Before you say e.g. "well the compiler should 'know' it's a
'namespace std' issue, I'll say that no, it cannot (and should not)
make such an assumption. I might want an identifer of my own named
e.g. 'cout', which I have every right to define, in either a 'global',
'file', 'namespace'*, or 'local' scope, and expect no problems until I
explicitly cause a conflict with a 'using' statement which brings
'std::cout' into scope.

(*) except namespace 'std', where the 'user' is not
allowed to define anything.


OP's problem is not an 'ambiguous' error message, but insufficient
background knowledge before using the compiler.

-Mike

 

[Mike Wahler]

It's been a little while, but I seem to recall that
including a file from the "builtin" include dirs is
done via:
#include <filename>
That tells the compiler to use its own include path(s).

But including a USER file is done via:
#include "filename"
That tells the compiler to use the include paths from
the compile commandline (or defaults)(or project/etc).

Try changing the < and > to " and " and see what
happens.

Please check your facts before making such suggestions.

-Mike

 

[ncstate]

Thanks for the help. the only thing that i seemed to find that worked
was to #include <iostream.h> and it gives me a depreciation message but
compiles and runs fine. is this normal for g++ 3.2.2?? it compiles fine
with #include <iostream> with g++ 2.8.1? should i just keep using the .h
extention and ignore the message?

 

[Artie Gold]

Thanks for the help. the only thing that i seemed to find that worked
was to #include <iostream.h> and it gives me a depreciation message but
compiles and runs fine. is this normal for g++ 3.2.2?? it compiles fine
with #include <iostream> with g++ 2.8.1? should i just keep using the .h
extention and ignore the message?

No, you should use <iostream> -- which is the proper header -- and
correct your *code*.

HTH,
--ag

 

[Mike Wahler]

Thanks for the help. the only thing that i seemed to find that worked
was to #include <iostream.h> and it gives me a depreciation message but
compiles and runs fine. is this normal for g++ 3.2.2?? it compiles fine
with #include <iostream> with g++ 2.8.1? should i just keep using the .h
extention and ignore the message?

No.

#include <iostream>

int main()
{
std::cout << "Hello\n";
return 0;
}

-Mike

 

[David Rubin]

Mike Wahler wrote:
[snip]

"'cout' undeclared." Exactly the case. How much more specific
could it be?

Before you say e.g. "well the compiler should 'know' it's a
'namespace std' issue, I'll say that no, it cannot (and should not)
make such an assumption.

I wasn't suggesting that.

OP's problem is not an 'ambiguous' error message, but insufficient
background knowledge before using the compiler.

This is more like it. After years of not using std::, I am sometimes
bewildered when the compiler can't find declarations I know
exist...somewhere.

/david

 

[ncstate]

Thanks for all the help.. Sorry I didn't catch on before. All of the
posts were helpful and appriciated.



Jeff

 

[MPBroida]

Please check your facts before making such suggestions.

Just looked in my "fact sack" and all looks
well. What facts are you unhappy with?

Mike