g++: compilation of header file requested

[blueblueblue2005]

Hi, here is an example I copied from Deitel C++ book. but when I
compile it, always get the above compilation error, no matter how I
change the include order, please help.

here is the files:
Note: this is to practice Proxy classes.

// Implementation. h

class Implementation {
public:
Implementation( int v) { this->v = v; }
void setValue(int v)
{
this->v = v;
}

int getValue() const
{
return v;
}

private:
int v;
};

// Interface.h

class Implementation;

class Interface {
public:
Interface(int);
~Interface();
void setValue(int);
int getValue() const;

private:
Implementation *ptr;
};

/* Interface.cpp */

#include "Implementation .h"
#include "Interface. h"

Interface::Inte rface(int v):ptr(new Implementation( v))
{ }

Interface::~Int erface() { delete ptr; }

void Interface::setV alue(int v){
ptr->setValue(v);
}

int Interface::getV alue() const {
return ptr->getValue();
}

/* t.cpp */

#include <iostream>

using namespace std;

#include "Interface. h"
#include "Implementation .h"

int main(){
Interface i(5);

cout << i.getValue() << endl;
i.setValue(19);
cout << i.getValue() << endl;
return 0;
}

# ============ this is Makefile
# Makefile
a.out: Implementation. h Interface.h Interface.cpp t.cpp
g++ Implementation. h Interface.cpp t.cpp
clean:
rm -f a.out
cleanall:
rm -f *.h *.cpp a.out

[Dietmar Kuehl]

blueblueblue200 5 wrote:

Hi, here is an example I copied from Deitel C++ book. but when I
compile it, always get the above compilation error, no matter how I
change the include order, please help.
Well, you might want to read the error message: it clearly says
that the compiler complains about the request that it should
compile a header file.
# ============ this is Makefile
# Makefile
a.out: Implementation. h Interface.h Interface.cpp t.cpp
g++ Implementation. h Interface.cpp t.cpp

The above line should read

g++ Interface.cpp t.cpp

instead.
--
<mailto:di***** ******@yahoo.co m> <http://www.dietmar-kuehl.de/>
<http://www.eai-systems.com> - Efficient Artificial Intelligence

[ambar.shome]

Hi,

May be you need to change your makefile. At the same time I dont
understand why r u defining the body of the functions within header
files like u did in Implementation. h. As far as my knowledge goes ".h"
files are for declaring function prototypes and variables only. We dont
write the body of the function within a header file. That might be the
reason why r u getting this compilation error.
blueblueblue200 5 wrote:

Hi, here is an example I copied from Deitel C++ book. but when I
compile it, always get the above compilation error, no matter how I
change the include order, please help.

here is the files:
Note: this is to practice Proxy classes.

// Implementation. h

class Implementation {
public:
Implementation( int v) { this->v = v; }
void setValue(int v)
{
this->v = v;
}

int getValue() const
{
return v;
}

private:
int v;
};

// Interface.h

class Implementation;

class Interface {
public:
Interface(int);
~Interface();
void setValue(int);
int getValue() const;

private:
Implementation *ptr;
};

/* Interface.cpp */

#include "Implementation .h"
#include "Interface. h"

Interface::Inte rface(int v):ptr(new Implementation( v))
{ }

Interface::~Int erface() { delete ptr; }

void Interface::setV alue(int v){
ptr->setValue(v);
}

int Interface::getV alue() const {
return ptr->getValue();
}

/* t.cpp */

#include <iostream>

using namespace std;

#include "Interface. h"
#include "Implementation .h"

int main(){
Interface i(5);

cout << i.getValue() << endl;
i.setValue(19);
cout << i.getValue() << endl;
return 0;
}

# ============ this is Makefile
# Makefile
a.out: Implementation. h Interface.h Interface.cpp t.cpp
g++ Implementation. h Interface.cpp t.cpp
clean:
rm -f a.out
cleanall:
rm -f *.h *.cpp a.out

[Dan Cernat]

blueblueblue200 5 wrote:

Hi, here is an example I copied from Deitel C++ book. but when I
compile it, always get the above compilation error

[snip]
What error? There in no error included in the body of the message. Make
sure to include your problem in the *body* of the message not only in
the subject line.

/Dan

[Dan Cernat]

blueblueblue200 5 wrote:

Hi, here is an example I copied from Deitel C++ book. but when I
compile it, always get the above compilation error

[snip]
What error? There is no error included in the body of the message. Make
sure to include your problem in the *body* of the message not only in
the subject line.

/Dan

[blueblueblue2005]

you are right, g++ Interface.cpp t.cpp works. but why when I include
Implementation. h in g++ command, it complains that it should compile a
header file??

[blueblueblue2005]

the reason I define the body of functions within header file is the
body is too small, as you see, just one line. and the reason I got
compilation of header file error is my Makefile.

Dietmar's reply indicated the error, I just dont know why I can't
include Implementation. h in g++ command.

[Paul]

blueblueblue200 5 wrote:

you are right, g++ Interface.cpp t.cpp works. but why when I include
Implementation. h in g++ command, it complains that it should compile a
header file??

You are not supposed to send header files to the compiler. Header files
are generally used to only define an interface to an implementation
file, object file, or library.
It is common to implement small functions and declare them 'inline' in
header files for convenience, or to declare bodies of small class member
functions so they don't get lost among much larger functions declared in
the counterpart cpp files.
Just send 'cpp' and 'o' files to the compiler, it will find the headers
through your #include directives.
--Paul

[blueblueblue2005]

Make sure to include your problem in the *body* of the message not only in
the subject line.

Ok, :-)

[Leon Mergen]

Hello,

On Mon, 2005-07-04 at 11:43 -0700, am*********@gma il.com wrote:

As far as my knowledge goes ".h" files are for declaring function
prototypes and variables only. We dont write the body of the function
within a header file. That might be the reason why r u getting this
compilation error.

As far as my knowledge goes, this is being done on a pretty common base.
For example, the Spirit parser ( http://spirit.sf.net/ ) is written
entirely in header files.

I know that header files are supposed to be for defining functions, but
isn't this rather for /other/ classes that include this class ? I mean,
as I see it, the strict separation between header files and source files
is because that way a compiler can look at a header, know what functions
a certain class accepts, and then parse one class accordingly... you do
not need a pure definition of the class YET... but what's so much
against it, if it's possible ? Sure, if a class includes a class that
tries to access member functions of the class including it (sheesh, what
a sentence :)), sure, you need separation between header and source so
it can be solved at compile-time... but why do you need to do this all
the time, especially for the simple functions the parent post is using ?

Regards,

Leon Mergen