Home » U++ Library support » U++ Core » Transfer Semantics - Initializer list and copy constructors
| Transfer Semantics - Initializer list and copy constructors [message #10459] |
Tue, 10 July 2007 15:33  |
captainc
Messages: 278
Registered: December 2006
Location: New Jersey, USA
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Experienced Member |
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I've been trying to get used to Upp NTL library and the pick semantics, an idea that I think is great, but still have a few questions.
Mainly, do initializer lists use deep copy/copy constructors? Also, the do Vector and Array Add() functions use copy constructors while the AddPick() functions do not?
I read the NTL tutorial and the Transfer Semantics section, but I think you should improve on this section with other examples of using it and not using it so that it is easier to grasp at first. I would love to see examples for appending Arrays or Vectors and an expanded explanation on the use of the Pick() and Copy() functions. This is all probably because I am still learning C++ as a language, and want to see it easy to learn and know the differences between standard implementations and NTL; especially for the cases where we use libraries that utilize standard library containers and we have to use them along with NTL containers.
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| Re: Transfer Semantics - Initializer list and copy constructors [message #11884 is a reply to message #10462] |
Sun, 30 September 2007 00:27  |
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forlano
Messages: 1185
Registered: March 2006
Location: Italy
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Senior Contributor |
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| 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).
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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
[Updated on: Sun, 30 September 2007 00:29] Report message to a moderator |
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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 |
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mirek
Messages: 13975
Registered: November 2005
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Ultimate Member |
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| 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).
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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
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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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