header file inclusion in c++

[Rahul]

Hi,

I often include the header files like the following,

#include <string.h>

However, i get a warning from the compiler to remove the .h and it
works fine with the following,

#include <string>

I also read an article which suggests to do the same, however it
doesn't claim any reason to do so... does anyone have any idea
regarding the same?

Thanks in advance!!!

[Mike Wahler]

"Rahul" <sa*****@yahoo.co.inwrote in message
news:b2**********************************@e6g2000p rf.googlegroups.com...

Hi,

I often include the header files like the following,

#include <string.h>

However, i get a warning from the compiler to remove the .h and it
works fine with the following,

#include <string>

I also read an article which suggests to do the same, however it
doesn't claim any reason to do so... does anyone have any idea
regarding the same?

The C++ standard library includes the (C90) standard C library,
so headers from both languages are available. The C++ library also
provides 'new' forms of the C headers, with the same names prepended
with letter 'c', and the '.h' dropped. The original names (with .h)
are also included for compatibility.

So. e.g. you can #include <stdio.hor <cstdiofor the same features.
Also the C names are encapsulated in namespace 'std' just as are the
C++ names (except macros).

Note that <string.h(and <cstring>) declare the 'C-style' string
operations (e.g. strcpy(), and <stringdeclares the C++ std::string type
and associated functions. Not the same thing at all.

Your questions cause me to ask which book(s) you're using to learn
C++ that don't explain this.

-Mike

[=?UTF-8?B?RXJpayBXaWtzdHLDtm0=?=]

On 2007-12-23 19:07, Mike Wahler wrote:

"Rahul" <sa*****@yahoo.co.inwrote in message
news:b2**********************************@e6g2000p rf.googlegroups.com...

>Hi,

I often include the header files like the following,

#include <string.h>

However, i get a warning from the compiler to remove the .h and it
works fine with the following,

#include <string>

I also read an article which suggests to do the same, however it
doesn't claim any reason to do so... does anyone have any idea
regarding the same?

The C++ standard library includes the (C90) standard C library,
so headers from both languages are available. The C++ library also
provides 'new' forms of the C headers, with the same names prepended
with letter 'c', and the '.h' dropped. The original names (with .h)
are also included for compatibility.

So. e.g. you can #include <stdio.hor <cstdiofor the same features.
Also the C names are encapsulated in namespace 'std' just as are the
C++ names (except macros).

Just to clarify, if you include the C++version of a C header (e.g. one
of those starting with c and without the .h) the functions are placed in
the std namespace, if you include the C version of the header (those
with .h) they are in the global namespace.

Also, AFAIK, the C++ headers (those not also in C) have never ended in
..h in standard C++, however before C++ was standardised using .h was
common so many compiler supports it for backwards compatibility.

--
Erik Wikström

[johanatan]

On Dec 23, 1:07 pm, "Mike Wahler" <[e-mail]:

Note that <string.h(and <cstring>) declare the 'C-style' string
operations (e.g. strcpy(), and <stringdeclares the C++ std::string type
and associated functions. Not the same thing at all.

I think this point could use a little expansion. Since the OP was
asking about <string.hvs. <string>, it should be pointed out that
this is an STL-specific requirement and the info provided about
standard C libs in C++, though useful, is slighty OT. Circa 1999, STL
dropped all the .h's from its include files and put them in an 'std'
namespace (std::vector, std::list, std::map, std::queue, etc.).

--Jonathan

[Jim Langston]

Rahul wrote:

Hi,

I often include the header files like the following,

#include <string.h>

However, i get a warning from the compiler to remove the .h and it
works fine with the following,

#include <string>

I also read an article which suggests to do the same, however it
doesn't claim any reason to do so... does anyone have any idea
regarding the same?

Thanks in advance!!!

As others are explaining, <string.his the c-style string functions. That
has been renamed to <cstringin the latest version of c++. <stringis the
c++ style string STL std::string. However, <stringalso includes some of
the c-style string functions also (not sure if it includes them all or not).

In either case, you would want to use <stringor <cstring>, but not the
depreciated <string.h>.

I'm just trying to point out that <stringis not the same as <string.h>,
but <cstringis the same as <string.halthough you'll probably need to use
the std:: prefix.

--
Jim Langston
ta*******@rocketmail.com

[johanatan]

On Dec 23, 5:48 pm, "Jim Langston" <[e-mail]:

As others are explaining, <string.his the c-style string functions. That
has been renamed to <cstringin the latest version of c++. <stringis the
c++ style string STL std::string. However, <stringalso includes some of
the c-style string functions also (not sure if it includes them all or not).

Well, I would assume that since his compiler said to replace
<string.hwith <string(and presumably, the code still compiled)
that he was only using STL string functionality and the C-style
functions that might have been included as a side effect. So, the
most direct answer to his question:

I also read an article which suggests to do the same, however it
doesn't claim any reason to do so... does anyone have any idea
regarding the same?

would be that STL dropped the .h's from its include files circa 1999.
This other C-style information that you guys have provided is just a
bonus IMHO. :-)