C / C++ / MFC

Richard MacCutchan16-Jan-11 7:04

Richard MacCutchan

16-Jan-11 7:04

It's initialising the object a of class A. In each case it is merely calling the object's constructor, and for primitive types (such as int) that just means setting them to the value in parenthesis.

Take a look at your C++ notes or manual for further discussion of instantiation, inheritance etc.

I must get a clever new signature for 2011.

Iain Clarke, Warrior Programmer

Iain Clarke, Warrior Programmer16-Jan-11 1:36

16-Jan-11 1:36

The : is called a colon by me - and many other people
It does different jobs in different places.

Ie:

switch (iValue)
{
case Bob: // Here is a label

   goto finished;
   ....
finished: // also a label
   return bIUseGotos;
}

bSuccess = (pFunction != NULL) ? pFunction->DoSomething () : false; // Here is something else - I think part of a ternary

And in your case, I'll pick a more common example:

class A
{
public:
   A (int i);
};

class B : public A
{
public:
   A ();
}

Now we make a constructor...

B::B ()
{
}

This will not compile - you will get a complaint about A not getting having a constructor with no parameters.
So, we need:

B::B ()
: A (7) // we're calling the A's constructor with a parameter of 7
{
}

The principle is exactly the same for member variables.

In your example, i's constructor is being called with 0. In the case of basic variables, there's an implicit constructor for this. It's not a real one.

As for what you'd call it, I have no idea. Inheritance operator?

Iain.

I am one of "those foreigners coming over here and stealing our jobs". Yay me!

Aescleal16-Jan-11 9:01

Aescleal

16-Jan-11 9:01

In the case you're asking about the colon marks the start of an initialiser list. These describe how to initialise a class's base class or member variables. Each element of the initialiser list has the syntax:

A( x, ... )

where A is either the name of the base class or the name of the member variable to be initialised and x,... is the list of arguments to the constructor of the base class or member.

I'd suggest grabbing a copy of "The C++ Programming Language" by Bjarne Stroustrup. He describes the initialisation of member objects and base classes in loads of detail in part 2 of the book. And explains why you'd prefer to write initialisers rather than making assignments in the body of a constructor.

Cheers,

Ash

How to get computer color setting?

moemass17-Jan-11 3:12

moemass

17-Jan-11 3:12

all i can recall is that the ":" is the resolution operator in c++ which basically mean that A() is a method in the A namespace
google it or buy yourself a good c++ book

includeh1015-Jan-11 20:37

includeh10

15-Jan-11 20:37

How to get computer color setting,
such as 256 colors and 16 or 32 bits?

Re: How to get computer color setting?

Andrew Brock15-Jan-11 20:53

Re: How to get computer color setting?

15-Jan-11 20:53

By using GetDeviceCaps(BITSPIXEL)

HDC hDC = GetDC(NULL);
int nBitsPerPixel = GetDeviceCaps(hDC , BITSPIXEL);
ReleaseDC(NULL, hDC );

includeh1016-Jan-11 2:47

includeh10

16-Jan-11 2:47

Hi, thanks, it works well.
the color setting looks like independent from HDC, is there a HDC independent function to obtain the value?

Re: How to get computer color setting?

Andrew Brock16-Jan-11 2:51

Sorting data using std::map or std::multimap

16-Jan-11 2:51

I dont completley understand the question.
Do you want a way to get it without using a HDC?
A quick google turned up http://stackoverflow.com/questions/1276687/how-can-i-find-out-the-current-color-depth-of-a-machine-running-vista-w7[^] which has a long way of doing it without a HDC

cmacgowan15-Jan-11 14:19

cmacgowan

15-Jan-11 14:19

Hi ...

Happy New Year. Hope everyone is ok. I have not been here for a while.

I have some contact lens data I'm trying to sort. I have some sort rules are static (hard-coded) followed by other rules form 'normal' rules

Here are the requirements:

1. First sort by Company and Product is a static order (hard-coded, non alphbetic)

Sample
o Company ProductName
--------------------------------------------------------------------
1. Ciba 1. Focus, 2. AirOptics, 3. Dailies, 4. then alphabetical.
2. Bausch & Lomb 1. PureVision, 2. LiquidEye, 3. Softlens then alphabetical.

2. Followed by Package size decending (80, 30 ...)

3. Followed by Base Curve decending (8.6, 8,0 ...)

4. Followed by Sphere decending (-0.5, 0.0, 1.0 ...)

In the end the result might look like the following

Sample data
CO PR PS BC Sp
-------------------------------
Ciba Focus 10 8.6 0.00
Ciba Focus 20 8.6 -0.25
Ciba Focus 20 8.6 -0.10
Ciba Focus 20 8.6 +0.25
Ciba Air 10 8.6 -0.25
Ciba Air 10 8.6 -0.10
Ciba Air 20 8.1 -0.25
Ciba Air 20 8.1 -0.10
Ciba Air 20 8.1 0.00
Ciba Air 20 8.6 +0.25
Ciba Air 20 8.6 +0.40

The data is contained in a struct with other data. The stuct is used in a map with a key. I am building a key to sort for the static requirments such as below.

The key contains a prefix at the front of the key to force the static sort (non alphabetical), followed by a suffix to make the key unique. Sample key: "1_1_Ciba_Focus Monthlys_4"

My plan to sort the other requirments is to take each of the other requirments (PackageSize, Base Curve and Sphere) and sort them against the previous element with the key.

Since I will be sorting the following agaist the Package Size (10, 20 ...) - maybe I should be using the multimap, as it might be easter to sort this stuff without having the unique ID at the end of key ??

With the key of "1_1_Ciba Focus" I would sort on the PackSize and then set the key to produce the correct sort

start: (std::multimap)
key: 1_1_Ciba Focus"
Sample data
CO PR Key
-------------------------------
Ciba Focus 1_1_Ciba Focus
Ciba Focus 1_1_Ciba Focus
Ciba Focus 1_1_Ciba Focus
Ciba Focus 1_1_Ciba Focus

Sample data
CO PR PS Key
-------------------------------
Ciba Focus 10 1_1_1_Ciba Focus
Ciba Focus 20 1_1_2_Ciba Focus
Ciba Focus 20 1_1_2_Ciba Focus
Ciba Focus 20 1_1_2_Ciba Focus

Thanks,
Chris
chris@macgowan.com

Andrew Brock15-Jan-11 18:08

15-Jan-11 18:08

Maps are sorted by the key, so you cant have them stored in the static order for 1.
Depending on how often you are adding to the list and to where i would recomend either a std::vector or std::list for storing the data in the static order

Your question is a little unclear, but if i'm reading it correctly you need something like this.

cmacgowan wrote:
4. Followed by Sphere decending (-0.5, 0.0, 1.0 ...)

The order there is ascending

#include <stdio.h>
#include <string>
#include <vector>
#include <map>

//save putting std:: infront of everything
using std::string;
using std::map;
using std::vector;

//This struct stores the data that is required for sorting
class ProductTypeKey {
	public:
		ProductTypeKey() { }
		ProductTypeKey(unsigned _nPackageSize, float _nBaseCurve, float _nSphere)
			: nPackageSize(_nPackageSize), nBaseCurve(_nBaseCurve), nSphere(_nSphere) { }

	public:
		unsigned nPackageSize;
		float nBaseCurve;
		float nSphere;
};

//"The data is contained in a struct with other data.". This struct stores "[the] other data"
typedef struct {
	//the other data you spoke of
} ProductTypeData;

struct MyItemCompare {
	bool operator()(const ProductTypeKey &mkLeft, const ProductTypeKey &mkRight) const {
		//Compare the package sizes, if they are not equal, then we are sorting by this key
		if (mkLeft.nPackageSize != mkRight.nPackageSize) {
			//greater than for decending order
			return mkLeft.nPackageSize > mkRight.nPackageSize;
		}
		//Compare the base curves, if they are not equal, then we are sorting by this key
		if (mkLeft.nBaseCurve != mkRight.nBaseCurve) {
			//greater than for decending order
			return mkLeft.nBaseCurve > mkRight.nBaseCurve;
		}
		//Compare the sphere, if they are not equal, then we are sorting by this key
		if (mkLeft.nSphere != mkRight.nSphere) {
			//less than for ascending order
			return mkLeft.nSphere < mkRight.nSphere;
		}
		//We will only make it here if the 2 products are identical from the data we are sorting on.
		return false;
	}
};

//This struct contains the information that is stored in static order
class Product {
	public:
		typedef map<ProductTypeKey, ProductTypeData, MyItemCompare> TypesMap;

	public:
		Product() { }
		Product(const string &_strCompany, const string &_strProduct)
			: strCompany(_strCompany), strProduct(_strProduct) { }
		void AddType(const ProductTypeKey &key, const ProductTypeData &data){
			colTypes.insert(TypesMap::value_type(key, data));
		}

	public:
		string strCompany;
		string strProduct;
		TypesMap colTypes; //this stores the data for this product that in sorted order
};

int main(int argc, char *argv[]) {
	Product prodCibaFocus("Ciba", "Focus");
	//Adding types before insert
	prodCibaFocus.AddType(ProductTypeKey(10, 8.6f, +0.00f), ProductTypeData());
	prodCibaFocus.AddType(ProductTypeKey(20, 8.6f, -0.25f), ProductTypeData());
	prodCibaFocus.AddType(ProductTypeKey(20, 8.6f, -0.10f), ProductTypeData());
	prodCibaFocus.AddType(ProductTypeKey(20, 8.6f, +0.25f), ProductTypeData());
	Product prodCibaAir("Ciba", "Air");
	vector<Product> colProducts;
	colProducts.push_back(prodCibaFocus);
	colProducts.push_back(prodCibaAir);
	//Adding types after insert. prodCibaAir is the 2nd item in the list (index 1)
	colProducts[1].AddType(ProductTypeKey(10, 8.6f, -0.25f), ProductTypeData());
	colProducts[1].AddType(ProductTypeKey(10, 8.6f, -0.10f), ProductTypeData());
	colProducts[1].AddType(ProductTypeKey(20, 8.1f, -0.25f), ProductTypeData());
	colProducts[1].AddType(ProductTypeKey(20, 8.1f, -0.10f), ProductTypeData());
	colProducts[1].AddType(ProductTypeKey(20, 8.1f, +0.00f), ProductTypeData());
	colProducts[1].AddType(ProductTypeKey(20, 8.6f, +0.25f), ProductTypeData());
	colProducts[1].AddType(ProductTypeKey(20, 8.6f, +0.40f), ProductTypeData());
	//now print them
	for (vector<Product>::const_iterator iProduct = colProducts.begin(); iProduct != colProducts.end(); ++iProduct) {
		for (Product::TypesMap::const_iterator iType = iProduct->colTypes.begin(); iType != iProduct->colTypes.end(); ++iType) {
			printf("%s %s %u %.02f %.02f\n", iProduct->strCompany.c_str(), iProduct->strProduct.c_str(),
				iType->first.nPackageSize, iType->first.nBaseCurve, iType->first.nSphere);
		}
	}
	return 0;
}

cmacgowan16-Jan-11 11:01

cmacgowan

16-Jan-11 11:01

Hi Andrew Brock,

Thanks for the response. I'll look at it and try it out.
Looks good.
I'll post a follow up.
Thanks,
Chris

Aescleal16-Jan-11 6:10

Aescleal

16-Jan-11 6:10

I'm not 100% sure what you're driving at but it looks as if you only want to use a map so you can synthesise a key and then use that to control the sort. The traditional way (at least in C++) to force a sort order in a collection is to implement operator< for the key (in a map) or the value (in a vector) that you're storing.

So if you've got a class with your contact lens data in try something like:

//contact_lens_data.h

class contact_lens_data
{
    // All the funkiness that's fit to print about contact lenses

    friend bool operator< (const contact_lens_data &left, const contact_lens_data &right );
};

//contact_lens_data.cpp

bool operator< (const contact_lens_data &left, const contact_lens_data &right )
{
    // Put the comparison in here, if left should appear towards the front of the sort order return true
}

Then you can store them in any collection and get the collation order you want using std::sort or the inserter for std::map.

Cheers,

Ash

Software Keyboard Simulator

cmacgowan16-Jan-11 11:02

cmacgowan

16-Jan-11 11:02

Thanks for the info
I'll check it out
Chris

RedDragon2k15-Jan-11 4:48

RedDragon2k

15-Jan-11 4:48

Hello,

I was just wondering whether it was possible to connect two PCs with a USB cable and simulate a keyboard on one of them. I know I could do this with a client/server system using DirectInput, but would it still be possible without installing any software on the target machine? If possible I would like to avoid using any micro-controller between the to PCs.
Any ideas whether that's possible or not?

Ben

jschell15-Jan-11 10:02

jschell

15-Jan-11 10:02

RedDragon2k wrote:
without installing any software on the target machine

Obviously something must run to capture the input on the target machine and inject it into the OS. So presumably you just mean that you don't want to install it first.

Should be possible to get the USB itself to do it. You might start by looking into how one boots an OS from a memory stick. Such articles have detailed info on how USB works.

Andrew Brock15-Jan-11 17:16

15-Jan-11 17:16

There is no standard for connecting PCs together with a USB cable that I know of, however if you write the driver for the computer sending the commands, you could make it appear as a keyboard to the other computer so you wont need anything on the remote computer.

I'm not too familiar with USB drivers, but if you get the Windows DDK[^] and take a look there are some sample USB drivers in the src folder.

loyal ginger15-Jan-11 17:25

loyal ginger

15-Jan-11 17:25

Your program should send out signal through the USB port you are using to connect to the target machine exactly the same signal a keyboard would send (when you use a USB keyboard). The target computer will simply believe that a USB keyboard is being plugged to the USB port. That means it's possible to achieve what you want to do. You need to work on the details, though. I believe you need to use Windows DDK to write programs to deal with USB.