C / C++ / MFC Discussion Boards

Ian Darling23-Dec-03 3:28

23-Dec-03 3:28

Do you mean converting an integer value into a string? If so, that's in the CP C++ FAQ here[^]

--
Ian Darling
"The moral of the story is that with a contrived example, you can prove anything." - Joel Spolsky

Re: Convert an int to char array rep

Anonymous23-Dec-03 4:21

Anonymous

23-Dec-03 4:21

No, more like binary rep only in char. I'm sending a stream of bytes.

Re: Convert an int to char array rep

nde_plume23-Dec-03 4:19

nde_plume

23-Dec-03 4:19

Alternatively (to Ian's suggestion) if you mean to treat an
integer as a four byte character array you can do so by casting:

int i = getValue();
char* p = reinterpret_cast<char*>(i);

However, that is a pretty scary thing to do, since obviously the
string will not be guaranteed to be null terminated (unless
i&0xFF is 0 on a big endian machine, or i&0xFF000000 is zero
on a little endian machine, and also assuming that sizeof(int) == 4)

Not recommended. Perhaps you could tell us what you are actually
trying to do.

Re: Convert an int to char array rep

Anonymous23-Dec-03 4:25

Anonymous

23-Dec-03 4:25

I'm trying to convert an integer value into an array of bytes. Char array is used cause it's exactly one byte. I have library func which sends bytes over a stream if given a pointer to char array head.

Re: Convert an int to char array rep

nde_plume23-Dec-03 9:08

nde_plume

23-Dec-03 9:08

There are couple of issues you should be concerned with here.
First of all, you need to send the integer in a representation
that all readers will accept. As you probably know, different
processor achitectures represent integers in different ways,
consequently, most likely the best representation would be a
simple ASCII stringL

void convertMe(int i)
{
char s[MAX_CHAR];
itoa(i, s, 10);
sendBytes(s);
}

where sendBytes is your sending function. If you don't care about
endian-ness, you could also send the bytes directly like this:

sendBytes(reinterpret_cast<char*>(&i), sizeof(i));

However this assumes that sendBytes is not designed to send a string,
but a block of memory (hence the second parameter which is the length
of the block to send.) If it is designed to send strings it will
fail quite often since any zero byte within the integer will terminiate
the string.

Re: Convert an int to char array rep

David Crow23-Dec-03 4:28

David Crow

23-Dec-03 4:28

Something like this comes to mind:

int nNum;
char cBytes[4];
 
cBytes[0] = (nNum >> 24) & 0xff;
cBytes[1] = (nNum >> 16) & 0xff;
cBytes[2] = (nNum >> 8) & 0xff;
cBytes[3] = nNum & 0xff;

Five birds are sitting on a fence.
Three of them decide to fly off.
How many are left?

Chart Solutions

Monty²23-Dec-03 2:38

Monty²

23-Dec-03 2:38

Does anyone know any good FREE Chart Component is can use on ASP

Live as if your were to die tomorrow. Learn as if you were to live forever.
-Mahatma Gandhi

I am new in VC++, can anyone help me?

LostRabbit23-Dec-03 1:22

LostRabbit

23-Dec-03 1:22

What function can I call to display the coordinates of the point? D'Oh! | :doh:

Re: I am new in VC++, can anyone help me?

Maximilien23-Dec-03 3:06

Maximilien

23-Dec-03 3:06

what point ? the mouse position ?

have a look at GetCursorPos

Maximilien Lincourt
"Never underestimate the bandwidth of a station wagon filled with backup tapes." ("Computer Networks" by Andrew S Tannenbaum )

Getting class information

Md Saleem Navalur23-Dec-03 1:18

Md Saleem Navalur

23-Dec-03 1:18

hi,,,,,,

Is there any tool available which will read the .h file and give me the class
information such as a listing of all the member functions, etc ?

Any help is appreciated.

Thanks in advance.

saleem

Re: Getting class information

Robert Kuster23-Dec-03 5:44

Robert Kuster

23-Dec-03 5:44

You might try DocBuilder[^]

RK

Element in a vector of set

Anthony_Yio23-Dec-03 1:03

Anthony_Yio

23-Dec-03 1:03

Hello, how do I access the element which resides in a vector of set. The codes are show below.

vector< set<int> > objSetVt;

set<int> objSet1;

objSet1.insert(2);
objSet1.insert(4);
objSet1.insert(2);
objSet1.insert(7);

set<int> objSet2(objSet1);
set<int> objSet3(objSet1);

objSetVt.push_back(objSet1);
objSetVt.push_back(objSet2);
objSetVt.push_back(objSet3);

vector< set<int> >::iterator objVtItr;

for(objVtItr = objSetVt.begin(); objVtItr < objSetVt.end(); objVtItr++)
{
//??? How to access the element now
//objVtItr[0][0] <-- this give compile error
}

Sonork 100.41263:Anthony_Yio

Re: Element in a vector of set

valikac23-Dec-03 5:49

valikac

23-Dec-03 5:49

In the example, objVtItr is an iterator, but inside the loop you are access the actual containers via [] operator.

One solution is to access the container directly.

std::set<<...>>::const_iterator iData = objSetVt[x].begin();

Kuphryn

Re: Element in a vector of set

Jijo.Raj23-Dec-03 17:45

Jijo.Raj

23-Dec-03 17:45

Hai,

I think the problem is simple. That for a vector class, "[]" operator is overloaded. But for set the "[]" operator is not overloaded. Wink | ;)

So access the member of vector by using [] operator and then use iterators to traverse throught the set.

Control doesnot show in the UIDeactivated mode

safee ullah23-Dec-03 0:58

safee ullah

23-Dec-03 0:58

guys..
As i wrote earlier..my control doesnot show up when i host the control in the test container...now this is only happening in the UIDeactivated mode..
how can i set my control to draw itself and show in the UIDeactivated mode inside the test container..?

thanks again

strange problem with activex control

safee ullah23-Dec-03 0:22

safee ullah

23-Dec-03 0:22

hi there..

guys i wanted to know if u have a control and u place it in a container, but the control doesnt show rather just a boundary rectangle is visible..but when i execute the container with the control..the container is visible..

is it something to do with designmode or something or something else??

thanks

Re: strange problem with activex control

Monty²23-Dec-03 1:12

Monty²

23-Dec-03 1:12

In the OnPaint of ur ActiveX Control you have to draw seperatly for Design mode as well

Live as if your were to die tomorrow. Learn as if you were to live forever.
-Mahatma Gandhi

Tricky Question

SiddharthAtw22-Dec-03 23:59

SiddharthAtw

22-Dec-03 23:59

class c{
public:
a();
b();
};

main()
{
class c *pc = 0;
pc->a() //works
}

class c{
int i;
public:
c(0):i=0;
a();
b();
};

main()
{
class c *pc = 0;
pc->a(); //doesn't work fires exception
}
why? Frown | :(

Re: Tricky Question

jhwurmbach23-Dec-03 0:14

jhwurmbach

23-Dec-03 0:14

Because you are invoking a function (a()) on a pointer that was specifically made invalid (set to 0).

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

Re: Tricky Question

Ian Darling23-Dec-03 0:16

Ian Darling

23-Dec-03 0:16

What's the definition of function a()?

Contrary to popular belief, while you can call a member function through a null pointer, it only works if you don't need to access any member variables or virtual functions (essentially, you don't need to dereference this).

If a() uses the i integer in the second example, then you are trying to access a variable through a dereferenced null pointer, which obviously will fall over.

--
Ian Darling
"The moral of the story is that with a contrived example, you can prove anything." - Joel Spolsky

Re: Tricky Question

Monty²23-Dec-03 1:08

Monty²

23-Dec-03 1:08

Bravo

Live as if your were to die tomorrow. Learn as if you were to live forever.
-Mahatma Gandhi

Re: Tricky Question

SiddharthAtw23-Dec-03 1:59

SiddharthAtw

23-Dec-03 1:59

Can U clarify on the matter of this. Please, I know what U told is correct but not able to understand 'you don't need to dereference this'.

Re: Tricky Question

Ian Darling23-Dec-03 2:14

Ian Darling

23-Dec-03 2:14

SiddharthAtw wrote:
Please, I know what U told is correct but not able to understand 'you don't need to dereference this'.

When you call a member function, that function has access to an intrinsic pointer called "this", which is a pointer the object you called the method on.

So in a hypothetical example:

// we have some class called c

int main()
{
  c myObject;
  myObject.a();  // the this pointer in a() below will be &myObject
  c *myPointer = new c;
  myPointer->a(); // the this pointer in a() below will point to the same object as myPointer
  c *myNullPointer = 0;
  myNullPointer->a(); // the this pointer in a() below is null, so accessing i through it will result in an access violation.
}

void c::a()
{
  // these two lines are equivalent.  When referring to a member variable in a
  // member function, there is an implicit "this->" before it.
  this->i = 1;
  i = 1;
}

--
Ian Darling
"The moral of the story is that with a contrived example, you can prove anything." - Joel Spolsky

Re: Tricky Question

SiddharthAtw23-Dec-03 18:11

SiddharthAtw

23-Dec-03 18:11

Thanx for making it Crystal Clear.

How can u initialize member variable while declaring???

abudu23-Dec-03 1:14

abudu

23-Dec-03 1:14

Not tricky, it is just basic. Second case will not work... how can you initalize the member variable 'i' while declaring it in the class c,u have to use constructor to initialize it. There is nothing to do with null class pointer. In both cases u have to define the functions a() and b() before calling them.

when going gets tough the tough gets going

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