Which constructor gets called while i create an array of , C/C++ Programming

Assignment Help:

Which constructor gets called while I create an array of Fred objects?


Related Discussions:- Which constructor gets called while i create an array of

What is structure, What is Structure? An Array is a data structure who...

What is Structure? An Array is a data structure whose elements are all of the similar data type. The structure is a data structure whose individual elements are able to differ

Using c language, I have a program and I want someone to fix it for me by u...

I have a program and I want someone to fix it for me by using basic c language program.

The Polishing Game, Byteland county is very famous for luminous jewels. Lum...

Byteland county is very famous for luminous jewels. Luminous jewels are used in making beautiful necklaces. A necklace consists of various luminous jewels of particular colour. Nec

Minimum shelf, At a shop of marbles, packs of marbles are prepared. Packets...

At a shop of marbles, packs of marbles are prepared. Packets are named A, B, C, D, E …….. All packets are kept in a VERTICAL SHELF in random order. Any numbers of packets with thes

D, drawbacks in assignments in engeenirng

drawbacks in assignments in engeenirng

Pointers, write short notes about void pointers

write short notes about void pointers

Described access privileges in c++? what is the default , A: In C++ the acc...

A: In C++ the access privileges are public, private and protected. The default access level assigned to members of a class is private. Private members of any class are accessible o

3/15/2013 5:58:52 AM

A: Fred''s default constructor

class Fred { public: Fred();

...

};

int main()

{

Fred a[10];  calls the default constructor 10 times

Fred* p = new Fred[10]; calls default constructor 10 times

...

}

If your class doesn''t contain a default constructor, you''ll get a compile-time error while you try to create an array by using the above simple syntax:

class Fred {

public:

Fred(int i, int j); suppose there is no default constructor

...

};

int main()

{

Fred a[10]; ERROR: Fred doesn''t contain a default constructor

Fred* p = new Fred[10]; ERROR: Fred doesn''t contain a default constructor

...

}

Though, even if your class already contain a default constructor, you must try to use std::vector instead of an array (arrays are evil). Std::vector allows you decide to use any constructor, not only the default constructor:

#include int main()

{

std::vector a(10, Fred(5,7));  the 10 Fred objects in std::vector a will be initialized along with Fred(5,7)

...

}

Although you have to use a std::vector instead of an array, there are times while an array may be the right thing to do, and for those, you may need the "explicit initialization of arrays" syntax. Here''s how:

class Fred {

public:

Fred(int i, int j);  assume there is no default constructor

...

};

int main()

{

Fred a[10] = {

Fred(5,7), Fred(5,7), Fred(5,7), Fred(5,7), Fred(5,7), // The 10 Fred objects are

Fred(5,7), Fred(5,7), Fred(5,7), Fred(5,7), Fred(5,7) // initialized using Fred(5,7)

};

...

}

Certainly you don''t contain to do Fred(5,7) for every entry you can put in any numbers you wish, even parameters or other variables.

Lastly, you can use placement-new to initialize manually the elements of the array. Warning: it''s unattractive: the raw array can''t be of type Fred, so you''ll require a bunch of pointer-casts to do things such as compute array index operations. Warning: its compiler- and hardware-dependent: you''ll require making sure the storage is aligned along with an alignment i.e. at least as strict as is needed for objects of class Fred. Warning: it''s boring to make it exception-safe: you''ll require to manually destructing the elements, by including in the case while an exception is thrown part-way through the loop which calls the constructors. But if you really wish to do it anyway, read up on placement- new. (BTW placement-new is like magic which is used inside of std::vector. The difficulty of getting everything right is still another reason to use std::vector.)

By the way, did I ever denote that arrays are wicked? Or did I denote that you have to use a std::vector unless there is a compelling cause to use an array?

 

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd