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Copy constructor

Hi,

Can someone please explain what a copy constructor does and how it's
useful? Thanks,

Terry

Jul 19 '05 #1
4 3206
"Terry" <te***@nospam.c om> wrote in message
news:3f******** @clarion.carno. net.au...
Hi,

Can someone please explain what a copy constructor does and how it's
useful? Thanks,

It constructs an object (like the regular c'tor) from an already
existing object. This way you avoid first constructing and then assigning
(ie. two steps, instead of one).

hth
--
jb

(replace y with x if you want to reply by e-mail)
Jul 19 '05 #2
A

Hi,

Can someone please explain what a copy constructor does and how it's
useful? Thanks,

It constructs an object (like the regular c'tor) from an already
existing object. This way you avoid first constructing and then assigning
(ie. two steps, instead of one).


can't you use use the assignment operator to copy? that should be one step
as well.

asasas


Jul 19 '05 #3
"A" <A@iprimus.com. au> wrote...

Hi,

Can someone please explain what a copy constructor does and how it's
useful? Thanks,

It constructs an object (like the regular c'tor) from an already
existing object. This way you avoid first constructing and then assigning (ie. two steps, instead of one).


can't you use use the assignment operator to copy? that should be one step
as well.


No. Assignment operator is useless when passing parameters by
value or returning by value is concerned. Those are the main
uses of the copy constructor.

Victor
Jul 19 '05 #4

"A" <A@iprimus.com. au> wrote in message
news:3f******** @news.iprimus.c om.au...

Hi,

Can someone please explain what a copy constructor does and how it's
useful? Thanks,

It constructs an object (like the regular c'tor) from an already
existing object. This way you avoid first constructing and then assigning (ie. two steps, instead of one).


can't you use use the assignment operator to copy? that should be one step
as well.

asasas


A a;
A b(a); // copy construct, one step
A c; // default construct, step 1
c = a; // assign, step 2

Creating a copy of an object using assignment uses two steps, first the
object is constructed, then it is assigned.

john
Jul 19 '05 #5

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