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Apr 15th, 2008

How can Can I copy the contents of one variable into another???

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Hi...

I am a bit new to programming, and I'm trying to learn C++. I was wondering if there was a way to copy the contents of one variable into another... So that, for example:

(Toggle Plain Text)

 
int x=5;
int y;
(Some fancy code here involving x and y);
(y=5 but it is not related at all to x. If x is assigned a value of 10438478234 later in the code, y will still equal 5)

The reason is that if I use variable assingment or pointers, and x changes, then so will y... If you please, list a code or method in order to achieve this data transfer

Thank you,

Farisnet

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Apr 15th, 2008

Re: How can Can I copy the contents of one variable into another???

int *y = &x; If x changes, then will *y

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Apr 15th, 2008

Re: How can Can I copy the contents of one variable into another???

If you want 2 variables to refer to the same data, you can also use references:

CPP Syntax (Toggle Plain Text)
   int x = 5;
   int &y = x;
 
   cout << x << "," << y << endl;
   x = 10;
   cout << x << "," << y << endl;
   y = 15;
   cout << x << "," << y << endl;
   int x = 5;
   int &y = x;
   
   cout << x << "," << y << endl;
   x = 10;
   cout << x << "," << y << endl;
   y = 15;
   cout << x << "," << y << endl;

output:
5,5
10,10
15,15

dougy83

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Apr 16th, 2008

Re: How can Can I copy the contents of one variable into another???

You missed my point. What I want is that if I change x, y is not affected.

Thank you!

Farisnet

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Apr 16th, 2008

Re: How can Can I copy the contents of one variable into another???

Ok...

c Syntax (Toggle Plain Text)
int x =3;
int y= 2;
cout << "x: " << x << " y: " << y << endl;
y=x;
cout << "x: " << x << " y: " << y << endl;
x=10;
cout << "x: " << x << " y: " << y << endl;
int x =3;
int y= 2;
cout << "x: " << x << " y: " << y << endl;
y=x;
cout << "x: " << x << " y: " << y << endl;
x=10;
cout << "x: " << x << " y: " << y << endl;

output:

C++ Syntax (Toggle Plain Text)
x: 3 y: 2
x: 3 y: 3
x: 10 y: 3
x: 3 y: 2
x: 3 y: 3
x: 10 y: 3

Nick Evan

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Apr 16th, 2008

Re: How can Can I copy the contents of one variable into another???

It does work like that?? But what about the "x=y" part, followed by "x=10"???? Doesn't that say "x has same value as y, and x is now 10" Doesn't that mean that y will also be 10?? (Please excuse my noobish questions, I'm just staring with this thing!!!)

Farisnet

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Apr 17th, 2008

Re: How can Can I copy the contents of one variable into another???

You sound like a mathematician, not a programmer.

In programming, x = 5 means set x to 5. y = x means set x to the value of y (the old value of x is discarded).

dougy83

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Apr 17th, 2008

Re: How can Can I copy the contents of one variable into another???

er...

look at it this way

when there is a = sign remember that it is an assignment operator not an "equal" sign

anything on the left is assigned to what is on the right

Quote ...

But what about the "x=y" part, followed by "x=10"???? Doesn't that say "x has same value as y, and x is now 10" Doesn't that mean that y will also be 10??

Looks like you read it wrong.
the only variable assignment he made was y = x

cheers

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Apr 17th, 2008

Re: How can Can I copy the contents of one variable into another???

Click to Expand / Collapse Quote originally posted by dougy83 ...

You sound like a mathematician, not a programmer.

In programming, x = 5 means set x to 5. y = x means set x to the value of y (the old value of x is discarded).

That should have been x = y. The complexity of the statement must have confounded me..

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