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Re: Transfer Semantics - Initializer list and copy constructors [message #11887 is a reply to message #11884]

Sun, 30 September 2007 08:32

mirek
Messages: 14267
Registered: November 2005

Ultimate Member

forlano wrote on Sat, 29 September 2007 18:27

luzr wrote on Tue, 10 July 2007 22:11

The simple rule: Do what you need. If you get crash because of broken pick semantics (the ASSERT in Vector with items = -1), use "deep copy variant" (<<= instead of =, constructor with additional int parameter (e.g. 1).

Hello,

for first time I needed to copy the content of a vector in another vector WITHOUT to destroy the original vector. This is my class:

class Person : Moveable<Person> {
	int  currentProposer;
	int  cursor;
  public:
	Index<int> preference;			
	int  RankProposer(int k);
        int  GetNext();						int  GetCurrentRank();					int  GetCurrentProposer();
        int  GetProposedTo();
	int  FindPosition(int k);
	void AcceptProposal(int k); 				
	String ToString() const { String s; for (int i=0; i<preference.GetCount();i++) s<<AsString(preference[i]) + ' '; return s; }
	Person() {currentProposer = 0; cursor = -1; } 
};

Then I declared two vectors:

Vector<Person> M, R;

After some operations made with M I would like to copy M in R. I used
R<<=M;
But the program crashed. Which is the correct syntax for this task?
Thanks,
Luigi

Unfortunately, this case is a little bit more complicated, you also have to provide deep copy operations for Person (which, frankly, is a tedious process, but there is no other way).

At minimum provide Person(const Person&, int) constructor that creates deep copy, and use DeepCopyOption template as base class to generate the rest.

Search

http://www.ultimatepp.org/srcdoc$Core$pick_$en-us.html

for "DeepCopyOption".

Mirek

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