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Please read this code and the question asked at the end.
class Point
{
private:
int x, y;
public:
Point();
Point(int x, int y); //constructor
int getX(); // getter
int getY(); // and
void setX(int x); // setters
void setY(int y); // functions
bool operator==(Point p) const; //overloaded == operator
~Point(); // destructor
};
class Box
{
private:
Point points[40];
public:
Point findPoint(Point p); //what should be the prototype of this function
};
Point Box::findPoint(Point p)
{
Point pTemp;
for(int i=0; i<40; ++i)
{
pTemp = points[i];
if( pTemp == p )
return pTemp;
}
return; // what to return here ?????????????
}
Look at the findPoint function. The responsibility of this function is to search in arrary
for the Point given and if function finds this Point, return it, otherwise if function does
not find the Point given it should return NULL. But I am unable to do it. I can achieve this
by changing the prototype of function like this
Point *findPoint(Point p);
butt I dont want to do this because it will break the conecpts of OOP and give access to
private data memeber.
The problem is if I return by value then I cant return NULL, so in user class or function,
I can not know whether the Point is found or not. and if I return the pointer, then I give
direct access to private data member.
Anybody help please !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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Why are you returning a 'Point' anyway? 
If it's found, they've already supplied the point in the first place, so the return result doesn't give them anything new except another point that matches the one they supplied.
Maybe a 'bool HasPoint( Point point )' method may suit your needs, or you could return an integer index into the array (and -1 if it doesn't exist)?
If you really do want to return a point for some reason then how about:
<br />
class Box<br />
{<br />
private:<br />
Point points[40];<br />
<br />
public:<br />
bool FindPoint( Point search, Point &result );<br />
};<br />
n!
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Thanks for the reply and reminding me my mistake.
Now consider the situation.
what if findPoint function now has this prototype
Point Box::findPoint(int x)
{
Point pTemp;
for(int i=0; i<40; ++i)
{
pTemp = points[i];
if(pTemp.getX() == x)
return pTemp;
}
return; // what to return here.
}
The purpose of the findPoint function is to find a Point which has its x data member equal to x provided. So, what to return
if the if condition not satisfied.
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Ahh ok, then I'd pass in a reference to be filled in and return a bool.
<br />
bool Box::FindPoint( int x, Point &result ) const<br />
{<br />
for ( int i = 0; i < 40; ++i )<br />
{<br />
if ( points[i].GetX() == x )<br />
{<br />
result = points[i];<br />
return true;<br />
}<br />
}<br />
return false;<br />
}<br />
n!
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Can we not use Java style here like this
this code fragment is of JAVA language
Point findPoint(int x);
so, in this case we can return null (cause null is a keyword in java) and also user defined types are reference types in java. My question now is
isnt there any alternative in C++ to this JAVA style other than provided by you???
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All objects in Java are reference types, you're not returning by reference you're returning by value here. C++'s class model is different to Java, the closest built in primitive to a Java reference (which may be null, as you said) is a pointer (C++ references may not legally be null), which you said you'd like to avoid.
The alternatives I can think of at the moment are:
Throw an exception, of course, but that's a bit heavy handed for a failed search
Return an integer index (with -1 meaning not found) and provide an index operator.
Write a RefResult templated wrapper and return one of those, but that doesn't give you anything more than you'd get returning a pointer (except more code).
My previous suggestion (returning bool).
I can only say that C++ isn't Java and if you prefer the Java style then use Java?
n!
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Thank you very much "n!"
I have decided to use your earliest suggestion (return bool). Your replies were really very much informative to me. I was really confusing Java and C++ memory management. This confusion is lowered very much by your replies.
Thank you.
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You can do several things. First I would change it to:
bool findPoint( Point& ptFound, Point p );
Another option is to keep your original code and set the returned Point to a value that would never occur in practice. eg. -1,-1. Then you could write:
IsPointValid( ptFound = findPoint( point ) )
You can and should also make the function const. You can also return a const ptr, which doesn't break your OOP rule. Solution 3. Use const wherever possible.
There you - pick 1.
Neville Franks, Author of ED for Windows. Free Trial at www.getsoft.com
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Hi , hwo can i get a drive size,
Please reply,
Thanks
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Have I lost my mind or is there no profiler in the Visual Studio .NET IDE?
If it is there, where is it? If not, does anyone know of a good one?
Thanks!
Marcus Spitzmiller
"Why must life be so hard? Why must I fail at every attempt at masonry?" - Homer
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I think you have knocked at a wrong door.
You might find your solution in VS.Net IDE section.
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duh - good point...Thanks
Marcus Spitzmiller
"Why must life be so hard? Why must I fail at every attempt at masonry?" - Homer
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I've a CEdit class. When you press 'a' from the keyboard, it writes 'a' in the control which is obvious.
The problem is that I want to change this behaviour. when I press 'a' from the keyboard, some other character e.g. 'b' should be written. I have a 2D array that has mappings of all the keyboard keys. Actually I am dealing with Unicode (a multilingual application).
Suppose I want to replace 'a' character with unicode 23456, which message should I handle.
I have tried WM_KEYDOWN and WM_CHAR and changed the virtual key code. but it did not worked.
In short, please tell me any way in which I can display 'b' in the edit control when 'a' is pressed.
Saqib.
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Try to override PreTranslateMessage
regards
modified 12-Sep-18 21:01pm.
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Thanks alot for your help Greg. I got my problem solved. PreTranslateMessage function handed the whole MSG structure to me. I traped the WM_CHAR message and changed the wParam to 'b' when it was actually 'a'.
if (pMsg->wParam == 'a')
pMsg->wParam = 'b';
Codeproject is really amazing site. Thankyou once again.
Saqib.
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You're welcome! 
regards
modified 12-Sep-18 21:01pm.
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I created a CStringArray to hold some text. Whenever I serialize the array, i noticed there are some garbage in the text file. How do I fix this. I want to write carriage returns and newlines. I'm using a CFile object.
Thanks
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Whenever you want text to appear on new line in file, use "\r\n" in a char type array or CString.
e.g. CString m_strLines;
m_strLines = "Line1.\r\nLine2\r\n";
I am not clear about the garbage that appeared in the file. Does the garbage characters appear at the end of your data or your data is not saved at all?
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Hi, I have no problems with the carriage and line feeds. I have garbage character in from of all the text strings. ie
Text1
Text2
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This is the class info from Serialize. The Serialize method stores the object info in a binary format, not a text format.
If you want to "serialize" your stringarray as a text file, you need to do this manually.
onwards and upwards...
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One solution is template function.
template <<typename t="">>
void mydesiredfunction(myclass<t> p);
Kuphryn
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Hello. I am a student and I am trying to write a library program for my school.
I have a big problem .... I don't know anything about doing a search engine for it! Can someone give me a website address which can help me or can someone post a code here or just give me the address of a tutorial (I searched for one but couldnt find).
Thank you!
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Well, if you are using ODBC to connect to a database, then SQL is what you'll use to communicate with the database. As far as doing pattern matching in SQL, take a look at the LIKE clause.
Example, if I wanted all records with a last name that started with A, I would write a SQL statement like such...
SELECT * FROM Users WHERE LastName LIKE 'A%'; For online info, here's a link...
http://www.codeproject.com/database/simple_odbc.asp[^]
Jeremy Falcon
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