Hello!
Is this too crazy or not?
Copy constructor: why can't I copy objects as if they were structs?
I have a set of simple objects (no string properties, just integers,
doubles) and I have to copy the same object millions of times.
So instead of writing in the copy constructor
property1=Sourc eObject.propert y1 can't I use memory copy functions to
do this faster?
Is this too stupid?
By the way, I'm a C++ newbie! But don't go easy on me just because...
;)
Bye! Thanks for your help and attention.
Jorge C. rd******@yahoo. com
Dec 22 '05
24  3628 
Victor Bazarov wrote: Jacek Dziedzic wrote:
> Victor Bazarov wrote:
A C++ practitioner should only use the term "bitwise" when talking about
the binary operators &, |, and ^, and the unary ~.
V
How about bitset::operato r[]? :>
That overloaded operator is called "indexing". I would expect a C++
programmer to be familiar with it under that name.
I know, but isn't the manner in which it indexes bit-wise?
- J.
Jacek Dziedzic wrote: Victor Bazarov wrote:
Jacek Dziedzic wrote:
> Victor Bazarov wrote:
A C++ practitioner should only use the term "bitwise" when talking
about
the binary operators &, |, and ^, and the unary ~.
V
How about bitset::operato r[]? :>
That overloaded operator is called "indexing". I would expect a C++
programmer to be familiar with it under that name.
I know, but isn't the manner in which it indexes bit-wise?
Well, as opposed to what? Indexing them logically? Indexing them whole?
Victor Bazarov wrote: You use sentences that are too long for my feeble brain.
class A { A(A&); }; // private copy c-tor
class B { A a; }; // not copy-constructible - 'a' cannot be copied
class C { B b; }; // no user-defined copy c-tor
void foo(C& c) {
C cc(c); // ill-formed
}
For the class C the compiler cannot create a copy-c-tor because 'b' does
not have "default" copy semantics because 'A' doesn't.. A program that
needs copy-construction of a 'B' or a 'C' is ill-formed.
class A { A(A&); }; // private copy c-tor
class B { A& a; }; // no user-defined copy c-tor, but 'a' can be copied
class C { B b; }; // no user-defined copy c-tor, but 'b' can be copied
void foo(C& c) {
C cc(c); // perfectly OK
}
'B' is perfectly copy-constructible, and so is 'C'. There is the issue
of constructing an object of type 'B' to begin with, but it's not what we
are talking about here.
Thank you for your great patience. You gave me explenation I tried to
ask for. Simply, I couldn't express my question as simple as I should.
Why? I'm not sure, may be I didn't understand the problem as I should
firt. Now, I know what you had in mind in your previous post.
Thank you
--
Mateusz Łoskot http://mateusz.loskot.net
rdc02271 wrote: Hello!
Is this too crazy or not?
Copy constructor: why can't I copy objects as if they were structs?
I have a set of simple objects (no string properties, just integers,
doubles) and I have to copy the same object millions of times.
So instead of writing in the copy constructor
property1=Sourc eObject.propert y1 can't I use memory copy functions to
do this faster?
Is this too stupid?
By the way, I'm a C++ newbie! But don't go easy on me just because...
;)
If you cannot afford a copy constructor, one will be appointed for
you before questioning.
The compiler generates a copy constructor if the user doesn't define
one. If there are no subobjects that themselves have copy constructors
it almost certainly does a very fast block copy of the object.
Victor Bazarov wrote: Jacek Dziedzic wrote:
Victor Bazarov wrote:
Jacek Dziedzic wrote:
> Victor Bazarov wrote:
> A C++ practitioner should only use the term "bitwise" when talking
> about
> the binary operators &, |, and ^, and the unary ~.
>
> V
How about bitset::operato r[]? :>
That overloaded operator is called "indexing". I would expect a C++
programmer to be familiar with it under that name.
I know, but isn't the manner in which it indexes bit-wise?
Well, as opposed to what? Indexing them logically? Indexing them whole?
As opposed to nothing, actually. What I meant to say was that
a "C++ practitioner" could easily use the word "bitwise" in
contexts other than involving "bitwise operators" that you
have mentioned.
My point was that a statement like
"the bitset::operato r[] overloaded operator allows for bitwise
access to the bitset" would be pretty legal.
But in fact I won't argue.
eot,
- J. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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A default copy constructor is created for you when you don't specify one
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Any others points i should know?
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