compile error - operator overloading

[Laxman]

==C.H <==
#include <fstream.h>
class C
{
public:
C(int i);
friend ofstream& operator<<(ofst ream& os, const C&);
};
------------------------------------------------------------
==B.H <==
#include <fstream.h>
#include "C.H"

class B
{
public:
friend ofstream& operator<<(ofst ream& os, const B&);
};
------------------------------------------------------------
==B.C <==
#include "B.H"

ofstream& operator<<(ofst ream& os, const B& b)
{
int i = 1;
os << i;
return os;
}
------------------------------------------------------------
CC -c B.C
"B.C", line 6: Error: Overloading ambiguity between
"std::basic_ost ream<char, std::char_trait s<char>>::opera tor<<(int)"
and "operator<<(std ::basic_ofstrea m<char, std::char_trait s<char>>&,
const C&)"

To make it easier I have trimmed down and kept only the necessary
code
to create the error.
BTW this works fine with g++ but fails with Sun Forte Compiler.
Any idea what the problem is ?

[Laxman]

Re: compile error - operator overloading

"MiniDisc_2 k2" <MattDelB@nospa m.com> wrote in message news:<FqEQa.539 9$zd4.3627@lake read02>...[color=blue]
> "Laxman" <pvlrao@yahoo.c om> wrote in message
> news:d882854d.0 307141133.6f424 ea7@posting.goo gle.com...[color=green]
> > ==C.H <==
> > #include <fstream.h>
> > class C
> > {
> > public:
> > C(int i);
> > friend ofstream& operator<<(ofst ream& os, const C&);
> > };
> > ------------------------------------------------------------
> > ==B.H <==
> > #include <fstream.h>
> > #include "C.H"
> >
> > class B
> > {
> > public:
> > friend ofstream& operator<<(ofst ream& os, const B&);
> > };
> > ------------------------------------------------------------
> > ==B.C <==
> > #include "B.H"
> >
> > ofstream& operator<<(ofst ream& os, const B& b)
> > {
> > int i = 1;
> > os << i;
> > return os;
> > }
> > ------------------------------------------------------------
> > CC -c B.C
> > "B.C", line 6: Error: Overloading ambiguity between
> > "std::basic_ost ream<char, std::char_trait s<char>>::opera tor<<(int)"
> > and "operator<<(std ::basic_ofstrea m<char, std::char_trait s<char>>&,
> > const C&)"
> >
> > To make it easier I have trimmed down and kept only the necessary
> > code
> > to create the error.
> > BTW this works fine with g++ but fails with Sun Forte Compiler.
> > Any idea what the problem is ?[/color]
>
> This may be unstandardized, I'm not sure, but I can tell you what the
> problem is.
> Your class C has a constructor which takes a parameter of an integer. Thus,
> i can be converted to a C if necessary. There is automatically an operator
> << for ofstream which takes an int, but you're also defining one which takes
> a C. As an int can be readily converted to a C, the compiler gets confused
> as to which one you want. A C cannot be converted to an int, so perhaps the
> solution is to cast it to a C. Also, perhaps explicitly typecasting it to an
> int would resolve the ambiguity to the compiler (even though it already is
> an int).[/color]
Thanks for replying. I did try to cast it explicitly to int but with
no luck!!

In the above example, I am trying to print a random datatype (int) but
my intent is to print a data member of B which is actually another
class, say A and C takes that same A as constructor's parameter.

[Laxman]

Re: compile error - operator overloading

"Steve Pinard" <sNO_SPAMpinard @zoominternet.n et> wrote in message news:<3f134b4a$ 1_6@corp.newsgr oups.com>...[color=blue]
> class C
> {
> C(int i)
> ...
> };
>
> As posted, declaring the constructor this way allows implicit conversion of
> an int to a C. This is usually NOT what you want the compiler to do for
> you, and is the source of some hard-to-track-down problems (case in point?).
>
> For constructors with only one parameter, I almost always use "explicit" to
> prevent the compiler from doing that:
>
> class C
> {
> explicit C(int i)
> ...
> };
>
> Have to credit Scott Meyers for this. I learned it from one of his
> Effective C++ books.
>
> --
> Steve Pinard
>
> "Dr. Spock is the only Star Wars character I know"
> - My Mom
>
>
>
>
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Thanks Steve. It works!!