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Control Flow

2 (2.2%)

Arrays, Strings, Pointers, and References

8 (9%)

Functions

4 (4.5%)

Basic object-oriented programming

30 (33.7%)

A bit more advanced OOP (Composition, Operator overloading, Inheritance, Virtual Functions)

18 (20.2%)

Templates

8 (9%)

Other (Explain)

4 (4.5%)

Working with files?  (Streams)

15 (16.9%)

Total Members Voted: 89

[winner]

I have a question why doesn't this work?

Code: [Select]

using namespace std;
struct foo{
virtual int baz (int a) {
return a;
}
};
struct bar: foo{
int baz () {
return baz(1);
}
};
int main(){}
when this does

Code: [Select]

using namespace std;
struct foo{
virtual int baz (int a) {
return a;
}
};
struct bar: foo{
int baz (int a) {
return a;
}
int baz () {
return baz(1);
}
};
int main(){}

[eerr]

That could be several problems. The error messages are helpful.

[Dasleah]

At first I was like for seeing HTML / CSS in a programming thread, and then I saw all the <tr> and <td>s and now I'm just

[winner]

for the first one

Code: [Select]

test.cpp: In member function ‘int bar::baz()’:
test.cpp:9: error: no matching function for call to ‘bar::baz(int)’
test.cpp:8: note: candidates are: int bar::baz() and the second compiles fine

I can get around it by just renaming the first function but I don't understand what the problem is because I thought that functions were identified by their arguments.

[eerr]

compiler error

Code: [Select]

using namespace std;
struct foo{
virtual int baz (int a) {
return a;
}
};
struct bar: foo{
int baz () {
return baz(1);
}
};
int main(){}

So if you change the

Code: [Select]

int baz () {
return baz(1);
}into

Code: [Select]

int WWW (){
return baz(1);
}It compiles fine?

[Normandy]

What's happening is called "Name Hiding". http://www.parashift.com/c++-faq-lite/strange-inheritance.html#faq-23.9 provides a good example of what is happening, why it is happening, and how to fix it.

[alway]

I'm currently making a small project with C++ and directX. I want to get input (or more specifically, which keys are pressed) in order to store said keys in a string; essentially text-editor functionality. Is there an easy way of doing this, or will I need several hundred 'if' statements using my normal direct input method of getting keypresses?

[qwertyuiopas]

First, a switch would be far better than a hundrred ifs.

Second, what sort of input do you have now? There is a win32 function that can convert scancodes to letters.

[alway]

I currently use the Direct Input code more or less unmodified from Frank D Luna's book "Introduction to 3D Game Programming With DirectX 9.0c, A Shader Approach"
As follows:

Spoiler (click to show/hide)

Code: [Select]

class DirectInput
{
public:
DirectInput(DWORD keyboardCoopFlags, DWORD mouseCoopFlags);
~DirectInput();

void poll();     //polls keyboard and mouse states, stores in variables
bool keyDown(char key);      //returns whether specified key is down using the mKeyboardState variable
bool mouseButtonDown(int button);
float mouseDX();       //change along x y and z axis of mouse
float mouseDY();
float mouseDZ();

private:
// Make private to prevent copying of members of this class.
DirectInput(const DirectInput& rhs);
DirectInput& operator=(const DirectInput& rhs);

private:
IDirectInput8*       mDInput;     //directInput

IDirectInputDevice8* mKeyboard;      //keyboard device
char                 mKeyboardState[256];   //array (not entirely sure how this array works) containing states of keyboard

IDirectInputDevice8* mMouse;          //mouse device
DIMOUSESTATE2        mMouseState;    //mouse states
};
Relevant member definitions:

Code: [Select]

void dInput::Poll()
{
HRESULT hr = mKeyboard->GetDeviceState(sizeof(mKeyboardState),
(void**)&mKeyboardState);

if(FAILED(hr))
{
ZeroMemory(mKeyboardState, sizeof(mKeyboardState));

hr = mKeyboard->Acquire();
}

hr = mMouse->GetDeviceState(sizeof(DIMOUSESTATE2), (void**)&mMouseState);

if(FAILED(hr))
{
ZeroMemory(&mMouseState, sizeof(mMouseState));
hr = mMouse->Acquire();
}
}

bool dInput::KeyDown(unsigned int key)
{
return (mKeyboardState[key] & 0x80) != 0;
}



With keyDown(char key); taking DIK key codes

How does one go about it in win32?

[qwertyuiopas]

That looks practically the same, for checking if a key is pressed. However, decoding keys as they are pressed in win32 is like this(At least the way I do it, in C):

Spoiler (click to show/hide)

Code: [Select]

unsigned char keys[256];

LRESULT CALLBACK winProc(HWND hwnd,UINT uMsg,WPARAM wParam,LPARAM lParam)
{
    ...
    switch(uMsg)
    {
      ...
      case WM_KEYDOWN:
      {
          static unsigned char out[2];
          GetKeyboardState(keys);
          if(ToAscii(wParam,MapVirtualKey(wParam,0),keys,(LPWORD)out,0)==1)
          {
              char key=out[0];
              input(key);
          }
          break;
      }
      ...
      default:
        break;
    }
    return DefWindowProc(hwnd,uMsg,wParam,lParam);
}


I don't know if directX lets you respond to window messages, but responding to them is the proper way to read input in the order it is pressed, unless you have something that does it for you.

[alway]

Awesome, thanks!

My program actually runs the directX on a window created with win32, so it shouldn't take too much effort to make it work now that I know what to put in the switch statement.

[qwertyuiopas]

When the if() fails, it means that it is a non-ASCII key, like VK_LEFT or whatever the one for shift or control is, so having an else to handle such cases is a good idea if you use them.

[Outcast Orange]

I'm doing a breadth-first search for a path between nodes A and B.

The ultimate goal is to end up with a path list (vector) that starts at node A and leads to node B.
So an example of a desired result would be { A, H, I, J, K, B } , where HIJK are connecting nodes.

With breadth first, the only way I can think of to keep track of the path a node is part of
 is to have each node store the ENTIRE path leading up to it, and copy it to new nodes.

Any alternate solutions?

I would prefer to not use an alternate method of path finding.

[alway]

You could use a form of linked list. Each node having links to the next nodes in each path and a link backwards to the previous node in the chain for ease of finding the final path. Thus giving you a data structure which literally looks like the diagram from the 'breadth first search' page on wikipedia. http://en.wikipedia.org/wiki/File:Breadth-first-tree.svg

[Outcast Orange]

I don't quite follow.

The object being searched is already a tree.
That does give me an idea though, which is probably what you meant.

I'll just have each node remember a temporary pointer to the node it came from,
 then the path can be followed back once it has been found.