Vectors - C / C++ / MFC Discussion Boards

George223-Sep-03 1:48

23-Sep-03 1:48

Hello everyone:

What is the difference the following two declarations, what are their advantage and

disadvantage? Or difference usage? Can anyone show me an example?

----------
typedef enum foo_ {

CON_1,
CON_2
}foo;
----------

and

----------
enum goo_ {

CON_1,
CON_2
}
----------

Thanks in advance,
Geo

Re: Question about enum in C/C++

567890123423-Sep-03 3:22

5678901234

23-Sep-03 3:22

http://www.codeguru.com/forum/showthread.php?s=&threadid=194304

Re: Question about enum in C/C++

George223-Sep-03 16:51

George2

23-Sep-03 16:51

Thanks, Alex buddy!

It is really a nice thread.

regards,
George

Re: Question about enum in C/C++

Mike Dimmick23-Sep-03 4:03

Mike Dimmick

23-Sep-03 4:03

In C, enums, structs and unions have their own namespaces. To use them elsewhere, you must say (for example) enum goo_.

The use of typedef adds a new name to the global type namespace, where the name can be used without qualifiers. Therefore you can declare a variable of type enum foo_ just by using the type name foo.

C++ removes this distinction; while enums may still be referenced by prefixing enum, this is no longer required. This may break some C code if the C code uses the same name for both an enum and a typedef. Therefore all of foo, foo_ and goo_ can be referenced directly. You can still refer to foo_ and goo_ as enum foo_ and enum goo_ respectively.

Examples:

foo bar; <font color="green">/* OK */</font>
foo_ bar2; <font color="green">/* C++: OK, C: error */</font>
enum foo_ bar3; <font color="green">/* OK */</font>
goo_ bar4; <font color="green">/* C++: OK, C: error */</font>
enum goo_ bar5; <font color="green">/* OK */</font>
 
struct foo { int i; }; <font color="green">/* C: OK, C++: error */</font>
int foo_; <font color="green">/* C: OK, C++: error (IIRC) */</font>

Re: Question about enum in C/C++

George223-Sep-03 16:49

George2

23-Sep-03 16:49

Thanks, Mike buddy!

I do not understand the why the following two statements are OK or error, can you give me a simple explanation?

Quote:
----------
struct foo { int i; }; /* C: OK, C++: error */
int foo_; /* C: OK, C++: error (IIRC) */
----------

regards,
Geo

Re: Question about enum in C/C++

Mike Dimmick24-Sep-03 9:11

Mike Dimmick

24-Sep-03 9:11

OK, let me try to explain namespaces again, a bit clearer this time hopefully!

Let's start with the global scope. In this scope, you can declare variables, functions and (through the typedef keyword) types.

In C, names that are introduced with the struct, union or enum keywords share another, separate, namespace which I'll call the structure namespace. Names can exist in both the global and the structure namespace with no problems. To access a name in the structure namespace, you must use the same keyword you used to declare it (i.e. if foo is an enumeration, you must use enum foo).

typedef can always be used to add a type name to the global namespace, whatever namespace the original type came from.

C++ changes the rules a bit. Types declared with the struct, union, enum and class keywords are still in a structure namespace; however, you no longer need to introduce them with the keyword when they're used.

Let's reproduce the example so it compiles:

 1 typedef enum foo_
 2 {
 3    FOO_BAR_1,
 4    FOO_BAR_2
 5 } foo;
 6  
 7 enum goo_
 8 {
 9    GOO_BAR_1,
10    GOO_BAR_2
11 };
12 
13 struct foo { int i; };
14 
15 int foo_;

The declaration at line 13 is NOT an error in C because the earlier foo at line 5 is a typedef name and hence is in the global namespace, while the declaration at 13 creates a foo in the structure namespace. It IS an error in C++ because it tries to introduce a new type with the same name.

However, I was wrong about line 15. It's OK in both C and C++. While you can't have a variable with the same name as a type in the global namespace, you're permitted to have one with the same name as a type in the structure namespace.

Results were compared with VC6 and with Comeau Computing's online compiler[^].

Note that I had to change the names of your enumerators (the values of the foo_ and goo_ enumerations). These are also added to the global namespace, and therefore would clash with each other if they had the same names.

Now to scopes: there is a 'global' and a 'structure' namespace within each scope that names can be declared in. A namespace using the C++ keyword is a named scope. Therefore you can refer to, for example, 'std::struct pair'.

Re: Question about enum in C/C++

George224-Sep-03 22:05

George2

24-Sep-03 22:05

Thanks, Mike buddy!

George

Vectors

bhangie23-Sep-03 0:56

bhangie

23-Sep-03 0:56

Hi there
I create a vector of size(10)
using a for loop to insert values into the vector

for(int i = 0; i < 10; ++i)<br />
 v.push_back(i + 0.1);<br />
<br />
//Display<br />
for(int i = 0; i < 10; ++i)<br />
 cout << v[i] << "\n";

Only display zero's on screen, When i dont put in an initial size the vector diplays what i want.
is it possible and to use v.size() rather than 10
in the for loops, but also displays zero's and warings
at compile time.
Am i doing something wrong!
Help! Big Grin | :-D

Regards bhangie

Re: Vectors

YaronNir23-Sep-03 0:58

YaronNir

23-Sep-03 0:58

is the vector a type of std::vector or is it CArray???

look at this example for std::vector -

int main( )
{
using namespace std;
vector <int> v1;

v1.push_back( 10 );
v1.push_back( 20 );

const int &i = v1.at( 0 );
int &j = v1.at( 1 );
cout << "The first element is " << i << endl;
cout << "The second element is " << j << endl;
}

notice that the item is retrieved with at() function and not with the operator [] .......

do the same for CArray using GetAt() method instead of at()

hope this helps

Yaron

Ask not what your application can do for you,
Ask what you can do for your application

Re: Vectors

jhwurmbach23-Sep-03 1:26

jhwurmbach

23-Sep-03 1:26

With
std::vector< double > v(10);
you create a vector of 10 elements with the value of 0.0
Later, with
v.push_back()
you add elements at the end of the vector.
When you display the first 10 items of the vector, you only show the zeros inserted at construction.
When you let your loop run to v.size(), (make i an unsigned int, or better still, std::vector< double >::size_type) it should display all you did put into the vector.

Hope this did clear things up for you

Who is 'General Failure'? And why is he reading my harddisk?!?

Re: Vectors

bhangie23-Sep-03 1:31

bhangie

23-Sep-03 1:31

Thanks YaronNir

std::vector
cleared up a few stuff
? 0.1,......up until 999.1
push_back(?)(or i + 0.1)
display all contents in vector

bhangie
regards

Re: Vectors

bhangie23-Sep-03 1:36

bhangie

23-Sep-03 1:36

Thanks oaks

got a better better understanding now!

bhangie

Re: Vectors

jhwurmbach23-Sep-03 1:48

jhwurmbach

23-Sep-03 1:48

Just as an excercise -
Here is how to use iterators for the display:

#include "stdafx.h"
#include "vector"
#include "iostream"
#include "string"

int _tmain(int argc, _TCHAR* argv[])
{
    std::vector< double > v(10);

    for(int i = 0; i < 10; ++i)
    v.push_back(i + 0.1);

    //Display
    std::vector< double >::iterator it = v.begin();
    while (it != v.end())
    {
        std::cout << *it << "\n";
        ++it;
    }

    std::string s;
    std::cin >> s;
}

Who is 'General Failure'? And why is he reading my harddisk?!?

Icon sizing problem

YaronNir23-Sep-03 0:56

YaronNir

23-Sep-03 0:56

i have a dilaog, on it i've placed a picture (from the resource controls)
i set the properties to icon.

the icon i have in the resources is 16x16, but when the dilaog is shown i get an icon image of 32x32.....why is that?

can any1 help me here? i need to display the 16x16 image (and i do not want to use a bitmap)

thanks in advanced

Yaron

Ask not what your application can do for you,
Ask what you can do for your application

Re: Icon sizing problem

RobJones23-Sep-03 6:05

RobJones

23-Sep-03 6:05

In the properties of the picture frame.. Go to styles and check the real size image.. It will still look large inside the development environment but once you execute the program you will see that it does in fact show up as 16x16.

Rob

Whoever said nothing's impossible never tried slamming a revolving door!

Re: Icon sizing problem

YaronNir23-Sep-03 6:11

YaronNir

23-Sep-03 6:11

thanks man Smile | :)

that really helped me!

Yaron

Ask not what your application can do for you,
Ask what you can do for your application

Re: Icon sizing problem

RobJones23-Sep-03 7:10

RobJones

23-Sep-03 7:10

no problem.. Smile | :)

Whoever said nothing's impossible never tried slamming a revolving door!

Changing the DC's offset

Zizilamoroso23-Sep-03 0:28

Zizilamoroso

23-Sep-03 0:28

CPaintDC dc(this);<br />
<br />
CRect r(0,0,10,10);<br />
CBrush brush(RGB(0,0,0));<br />
<br />
dc.FillRect(&r,&brush);<br />

This piece of code draws a filled rectangle at position 0,0.

How can I change the offset of the DC, that the rectangle will paint at, for instance, (x50,y50), without changing the CRect object itself?

I've tried some of the OffsetViewportOrg and SetWindowOrg methods, but I can't seem to make it work. It only changes the clip region.

I've tried SetBrushOrg too, together with Unrealize and SelectObject, but that doesn't change anything at all. If I read the msdn right, this is the function to use! But how?

How can I change the DC's offset?

using: [VISUAL STUDIO 6.0 sp5] [WIN98/2]

Re: Changing the DC's offset

vcplusplus23-Sep-03 3:14

vcplusplus

23-Sep-03 3:14

Did you try SetViewportOrg()?

Did you check your "Mapping Modes"?

Remember (0,0) is the upper left corner of the screen and the default mapping mode is MM_TEXT. This means X+ goes from left to right and y+ goes from top to bottom.

The scribble tutorial might give you some ideas.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vctutor98/html/_gs_scribble_tutorial.asp

Re: Changing the DC's offset

Zizilamoroso23-Sep-03 3:29

Zizilamoroso

23-Sep-03 3:29

dwccgc wrote:
Did you try SetViewportOrg()?

Yes, it only moves the clip rectangle. The rectangle itself is still painted at 0,0.

dwccgc wrote:
Did you check your "Mapping Modes"?

Mapmode is 1 (==MM_TEXT).

I think I have to use the SetBrushOrg, but that doesn't seem to work.

using: [VISUAL STUDIO 6.0 sp5] [WIN98/2]

Re: Changing the DC's offset

vcplusplus23-Sep-03 7:21

vcplusplus

23-Sep-03 7:21

I found some old code where I draw a Polygon. I use CClientDC instead of CPaintDC.

CMyView::OnDrawItem(int nIDCtl, LPDRAWITEMSTRUCT lpDrawItemStruct)
{

   CClientDC dc(this);
   ..
   ..
   CRect rcArea(lpDrawItemStruct->rcItem);
   rcArea.DeflateRect(20, 20);
   dc.SetViewportOrg(rcArea.left, rcArea.bottom);
   ..
   ..
   dc.Polygon(PolyPoints.pt, PolyPoints.nCoord);
   ..
   ..
}

Did you have any luck with that MS Scribble Link I left on the previous message?

Re: Changing the DC's offset

Zizilamoroso24-Sep-03 0:08

Zizilamoroso

24-Sep-03 0:08

I'll try it.

No, I don't have the examples, and there's no download at that page.

using: [VISUAL STUDIO 6.0 sp5] [WIN98/2]

Re: Changing the DC's offset

vcplusplus24-Sep-03 1:56

vcplusplus

24-Sep-03 1:56

Here is a link to the sample files;

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vcsample98/html/_sample_mfc_scribble.asp

You can also find the samples on your MSDN Library Disks

Good Luck

Re: Changing the DC's offset

Zizilamoroso24-Sep-03 5:25

Zizilamoroso

24-Sep-03 5:25

dwccgc wrote:
You can also find the samples on your MSDN Library Disks

I know, but I don't have the disks either...

But, meanwhile, I found a solution (workaround).

Instead of this:

CPaintDC dc(this)<br />

Use this:

PAINTSTRUCT ps;<br />
CDC* pDC=NULL;<br />
pDC=BeginPaint(&ps);<br />
<br />
...<br />
<br />
EndPaint(&ps);<br />

With the second code, the DC's offsets work the way they should. I don't know why they don't work with CPaintDC (nor CClientDC).

using: [VISUAL STUDIO 6.0 sp5] [WIN98/2]

SAS Window: Winlogon.exe Application error.

rohit.dhamija22-Sep-03 23:42

rohit.dhamija

22-Sep-03 23:42

Dear ALL,

I am developing an application for Windows 2000 in MFC VC++ Version 6.0.

My application runs as an interactive service.

I am using a dll in my program which is used to hide given key(s) from the registry. The program works fine and hides the given keys from registry. But when i log off my system and login, the following error occurs:
...............................
SAS Window: Winlogon.exe Application error.
The instruction at "0x01007f2d" refereced memory at "0x00006c". The memory could not be read. Click ok to close and cancel to debug.
...............................
On clicking ok the system restarts.

I think I need to free the dll before logging out. So I tried FreeLibrary in QueryEndSession, but it didnot helped.
Is there any other way to free the dll.

Or any other way out to solve the problem ?
The program is working fine when I restart and login (probably because at that time the dll is freed and loaded again,, but the same is not in case of log off and log in)

Thanks
Rohit Rose | [Rose]

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