Re: C++ Datatypes and OS Datatypes :: C++ - C / C++ / MFC Discussion Boards

Re: Advanced C++ Books

monrobot138-Dec-02 12:06

monrobot13

8-Dec-02 12:06

Thanks everyone for the replies.

- monrobot13

Re: Advanced C++ Books

Joe Woodbury9-Dec-02 19:39

Joe Woodbury

9-Dec-02 19:39

Check out Scott Meyers' "Effective C++" books.

C++ Datatypes and OS Datatypes :: C++

valikac7-Dec-02 8:40

valikac

7-Dec-02 8:40

Hi.

In general, is it more extensible to implement core C++ datatypes in 32bits and 64bits operating system, or should you implement the OS specific datatypes? For example, under Windows you can implement a DWORD (32bits unsigned integer). A DWORD is equal to C++ unsigned long.

I would like to know what is most extensible in terms of C++ design and implementation?

Lastly, what is the point of an int datatype in 32bits and 64bits OS? In 32bits OS, an int is equal to a long.

Thanks,
Kuphryn

Re: C++ Datatypes and OS Datatypes :: C++

Alvaro Mendez7-Dec-02 10:23

Alvaro Mendez

7-Dec-02 10:23

Here's what I've learned when dealing with the int and long data types in C++:

1. int was designed to be as large as what the CPU can handle most efficiently. In Win16 or Win32, int is 16 or 32 bits. in 32-bit UNIX systems int is 32 bits.

2. On 64-bit systems (Win64 or UNIX) int is also 32 bits, I guess to make it easier to port 32-bit apps.

3. long is 32 bits in Win16 and Win32, as well as 32-bit UNIX.

4. On Win64, long is also 32 bits, whereas on UNIX, it's 64 bits (which is what you'd expect, and how it's represented in .NET and Java).

So my suggestion, for the sake of simplicity and portability, stick with int -- don't use long.

Regards,
Alvaro

Well done is better than well said. -- Benjamin Franklin
(I actually prefer medium-well.)

Re: C++ Datatypes and OS Datatypes :: C++

Maximilien7-Dec-02 10:41

Maximilien

7-Dec-02 10:41

long is ( or was ?! ) a size qualifier for the int at the time of 16bits apps. ( samething for short ).

long and short are not really types!

Alvaro Mendez wrote:
4. On Win64, long is also 32 bits, whereas on UNIX, it's 64 bits (which is what you'd expect, and how it's represented in .NET and Java).

Are you sure ? I thought the int would be "scaled" according to the CPU ?

Max.

Re: C++ Datatypes and OS Datatypes :: C++

Michael Dunn7-Dec-02 14:23

Michael Dunn

7-Dec-02 14:23

Maximilien wrote:
long and short are not really types!

although everyone treats them as such. No one ever writes signed long int when long works just as well.

--Mike--
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Re: C++ Datatypes and OS Datatypes :: C++

Nemanja Trifunovic7-Dec-02 16:53

Nemanja Trifunovic

7-Dec-02 16:53

Maximilien wrote:
Are you sure ? I thought the int would be "scaled" according to the CPU ?

No. AFAIK, int remains 32-bit on Win64.

Beer | [beer]

Re: C++ Datatypes and OS Datatypes :: C++

Gary R. Wheeler8-Dec-02 2:33

Gary R. Wheeler

8-Dec-02 2:33

I believe the 64-bit CPU's coming out of Intel are still 32 bits wide in terms of their 'native' word size, but 64 bits in terms of memory addressing. int therefore stays 32 bits in Win64.

Software Zen: delete this;

Printing HTML progmatically

Darroll Walsh7-Dec-02 1:13

Darroll Walsh

7-Dec-02 1:13

I wrote an app that creates a web page. Now they want to print it out. The problem comes that the settings for everyones printing is set differently, ie margins, header/footer, and if print background is selected. Is there a way to send IE the paramiters I want to print for this page? Thanks in advance.

Darroll

Re: Printing HTML progmatically

Gary Wheeler7-Dec-02 4:58

Gary Wheeler

7-Dec-02 4:58

I've got a control derived from the browser. My printing code looks like this -

HRESULT hr;

BSTR        header_BSTR = ::SysAllocString(L"&w&b&b&p");
VARIANT     header_variant;

VariantInit(&header_variant);
V_VT(&header_variant)   = VT_BSTR;
V_BSTR(&header_variant) = header_BSTR;

BSTR        footer_BSTR = ::SysAllocString(L"&d &t");
VARIANT     footer_variant;

VariantInit(&footer_variant);
V_VT(&footer_variant)   = VT_BSTR;
V_BSTR(&footer_variant) = footer_BSTR;

long index;

SAFEARRAYBOUND  parameter_array_bound[1];
SAFEARRAY       *parameter_array = NULL;

parameter_array_bound[0].cElements = 2;
parameter_array_bound[0].lLbound   = 0;

parameter_array = SafeArrayCreate(VT_VARIANT,1,parameter_array_bound);

index = 0;
hr = SafeArrayPutElement(parameter_array,&index,&header_variant);

index = 1;
hr = SafeArrayPutElement(parameter_array,&index,&footer_variant);

VARIANT parameter;
VariantInit(&parameter);
V_VT(&parameter)    = VT_ARRAY | VT_BYREF;
V_ARRAY(&parameter) = parameter_array;

hr = _Browser->ExecWB(OLECMDID_PRINT,OLECMDEXECOPT_DONTPROMPTUSER,&parameter,NULL);

if (!SUCCEEDED(hr)) {
    VariantClear(&header_variant);
    VariantClear(&footer_variant);
    if (parameter_array != NULL) {
        SafeArrayDestroy(parameter_array);
    }
}

This code sets the header and footer for the page and then prints it. The _Browser value points to the IWebBrowser2 interface for the control. If I remember correctly, I found this stuff in an example in the MSDN.

Software Zen: delete this;

CString Vs std::string

Anonymous7-Dec-02 0:34

Anonymous

7-Dec-02 0:34

With CString, we can perform an operation something like:

CString strMarks;
strMarks.Format("I got %d marks",marks);

Can we perform similar operation using std::string ??? If yes, then how ???

Re: CString Vs std::string

Nitron7-Dec-02 4:37

Nitron

7-Dec-02 4:37

Try this:

char buffer[200] = {0};
std::string str = "";
int i = 9;
sprintf(buffer, "\n\nThis is number: %d\n\n", i);
str = buffer;
printf(str.c_str());

- Nitron

"Those that say a task is impossible shouldn't interrupt the ones who are doing it." - Chinese Proverb

Re: CString Vs std::string

Roman Fadeyev7-Dec-02 5:01

Roman Fadeyev

7-Dec-02 5:01

Unfortunately, you can't. In concept of C++ std library you must use streams (like as stdout, stdin and etc). This method was perfectly described by Alexandrescu in his book "Modern C++...". But personally I like to use old good method as Format. And I have invented my own function. May be it will be useful for you

string_smart Format(cstr szText,...)
{
	cstr  szPtr=szText;
	size_t lLen;
	//Calculating Average length
	for (lLen=0;*szPtr; ++szPtr,(*szPtr=='%') ?lLen+=10:lLen++);

	string_cstr strRes(++lLen);
	
	va_list marker;
	va_start( marker, szText);     
	
	while (_vsnprintf(strRes.buffer(),strRes.buffer_size()-1,szText,marker) <0 ) 
		strRes.reserve(strRes.buffer_size()*2);

	//_ASSERTE( _CrtCheckMemory( ));
	strRes.buffer()[strRes.buffer_size()-1]='\0';	//Don't remove this line!
	strRes.recalc_len();						
									

	va_end( marker );              
	
	return strRes;
}

This function works with my class string_smart, but it is not hard to remake it for std::string

Re: CString Vs std::string

Michael Dunn7-Dec-02 5:56

Michael Dunn

7-Dec-02 5:56

Yes you can, using the stringstream class:

#include <string>
#include <sstream>
 
ostringstream strm;
string strMarks;
 
  strm << "I got " << marks << " marks" << ends;
  strMarks = strm.str();

--Mike--
Friday's GoogleFight results: Britney Spears 2,190,000 - Erica Weichers 23 Frown | :(

1ClickPicGrabber - Grab & organize pictures from your favorite web pages, with 1 click!
My really out-of-date homepage
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Re: CString Vs std::string

Nemanja Trifunovic7-Dec-02 17:25

Nemanja Trifunovic

7-Dec-02 17:25

I would just rearange it a little:

#include <string>
#include <sstream>
std::ostringstream strm;
strm << "I got " << marks << " marks" << std::ends;
std::string strMarks = strm.str();

MIN/MAX values of Datatypes

Anonymous7-Dec-02 0:30

Anonymous

7-Dec-02 0:30

How can we find the min / max values of a particular data type:

ex.. what is the minimum or maximim value, that can be represented by DWORD

Re: MIN/MAX values of Datatypes

geo_m7-Dec-02 2:09

geo_m

7-Dec-02 2:09

try these:

<br />
ULONG_MAX,<br />
LONG_MAX, LONG_MIN...<br />

see limits.h in MSVC

File Properties in Windows 2000

Bats7-Dec-02 0:15

Bats

7-Dec-02 0:15

Has anyone noticed the "Summary" tab in the file-properties dialogue (RMB on some file, for e.g a .doc or a .mp3)?
There are entries for things like "Title", "Category", "Comments" etc

You cannot use these items in a normal search, so my question is how to access these extra properties of a file programatically so that one could search for all files that (say) have a "Category" of "BACKUP:OK" for e.g.

It's like the file-system is a Table in Access and these are 'fields' but you can't use them for filtering properly.

Hope there is some idea out there!

Bats
;}

Re: File Properties in Windows 2000

Anonymous7-Dec-02 1:29

Anonymous

7-Dec-02 1:29

http://support.microsoft.com/default.aspx?scid=KB;en-us;q186898

Re: File Properties in Windows 2000

Anonymous7-Dec-02 1:40

Anonymous

7-Dec-02 1:40

Thanks for the link - I am looking at it now !
Bats
:}

Re: File Properties in Windows 2000

Anonymous7-Dec-02 1:52

Anonymous

7-Dec-02 1:52

Ok - compiled that MS example and it works fine for MS type apps, but not for anyhing else. (e.g mp3, oggs)
Is there a more general way to access these 'extra' properties via C++ ?

Thanks
Bats
:}

* versus **

verbatin6-Dec-02 23:28

verbatin

6-Dec-02 23:28

One thing that I haven't seemed to get is the difference between *variable and **variable. Can anybody tell me the difference? Thanks. Laugh | :laugh:

Re: * versus **

Christian Graus7-Dec-02 0:20

Christian Graus

7-Dec-02 0:20

One is a pointer, the other is a pointer to a pointer.

int * n;

represents the memory address where space is allocated for an int.

int ** n;

represents the memory address which holds a memory address which has enough space for an int. Therefore with a ** you can create a 2D array.

int **n = new int * [20];

for (int i = 0; i < 20; ++i)
n[i] = new int [10];

Christian

No offense, but I don't really want to encourage the creation of another VB developer. - Larry Antram 22 Oct 2002

C# will attract all comers, where VB is for IT Journalists and managers - Michael P Butler 05-12-2002

Again, you can screw up a C/C++ program just as easily as a VB program. OK, maybe not as easily, but it's certainly doable. - Jamie Nordmeyer - 15-Nov-2002

Re: * versus **

verbatin7-Dec-02 4:10

verbatin

7-Dec-02 4:10

Thank you. I know what a pointer is, but the ** was what was confusing to me. That makes a lot of sense then - basically in your above example you're allocating enough space for your second pointer to reference 20 other integers, and then set each of those integers to be arrays with ten elements each. That was very helpful.

Re: * versus **

Anonymous7-Dec-02 0:34

Anonymous

7-Dec-02 0:34

I am new to C++ but:
*x is a pointer. x is actually an address. *x means "look inside that address"

so **x is just *(*x) - do the brackets first : ("look inside" x) and then do it again.

so if x was address:1776 then *x gives as some other value - say 2789 (the contents of 1776) and then * again looks inside 2789.
In old basic terms its peek(peek(x)) and in (bad) assembly its [[ax]]

Right, that confused even me!

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