assigning values to structure members

[Pushkar Pradhan]

I have a struct like this:
struct point {
int x;
int y;
};

Then I need to assign a certain point "=" another pt.
eg.
struct point p1, pArr[10];

/* initialize all pts. */
Now assign p1 to a certain element of pArr, this is how I did and it
works fine.
p1 = pArr[someIndex];

However, I just read my C book again and it says this stuff must be done
like this actually:
p1.x = parr[someIndex].x;
p1.y = parr[someIndex].y;

Can anybody tell if I should continue with the former code or should I
make changes?
Pushkar Pradhan

[Sheldon Simms]

On Sun, 16 Nov 2003 00:12:05 -0600, Pushkar Pradhan wrote:

I have a struct like this:
struct point {
int x;
int y;
};

Then I need to assign a certain point "=" another pt.
eg.
struct point p1, pArr[10];

/* initialize all pts. */
Now assign p1 to a certain element of pArr, this is how I did and it
works fine.
p1 = pArr[someIndex];

However, I just read my C book again and it says this stuff must be done
like this actually:
p1.x = parr[someIndex].x;
p1.y = parr[someIndex].y;

Please tell us the name of the C book so that we can all avoid it.
What you have done is fine.

[Richard Heathfield]

Sheldon Simms wrote:

On Sun, 16 Nov 2003 00:12:05 -0600, Pushkar Pradhan wrote:

I have a struct like this:
struct point {
int x;
int y;
};

Then I need to assign a certain point "=" another pt.
eg.
struct point p1, pArr[10];

/* initialize all pts. */
Now assign p1 to a certain element of pArr, this is how I did and it
works fine.
p1 = pArr[someIndex];

However, I just read my C book again and it says this stuff must be done
like this actually:
p1.x = parr[someIndex].x;
p1.y = parr[someIndex].y;
Please tell us the name of the C book so that we can all avoid it.

Careful. Maybe he has misread the book. (This has happened before in clc -
someone has said "my book says <foo>" when in fact it says <not foo>).
What you have done is fine.

Agreed.

--
Richard Heathfield : bi****@eton.powernet.co.uk
"Usenet is a strange place." - Dennis M Ritchie, 29 July 1999.
C FAQ: http://www.eskimo.com/~scs/C-faq/top.html
K&R answers, C books, etc: http://users.powernet.co.uk/eton

[Robert Stankowic]

"Pushkar Pradhan" <pu*****@gri.msstate.edu> schrieb im Newsbeitrag
news:3F**************@gri.msstate.edu...

I have a struct like this:
struct point {
int x;
int y;
};

Then I need to assign a certain point "=" another pt.
eg.
struct point p1, pArr[10];

/* initialize all pts. */
Now assign p1 to a certain element of pArr, this is how I did and it ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ works fine.
p1 = pArr[someIndex];

No :)
pArr[someIndex] = p1;
at least your text says so (if my english did not get into the way :).

However, I just read my C book again and it says this stuff must be done
like this actually:
p1.x = parr[someIndex].x;
p1.y = parr[someIndex].y;

Can anybody tell if I should continue with the former code or should I
make changes?

The assignment is fine (in both directions)

Robert

[CBFalconer]

Richard Heathfield wrote:

Sheldon Simms wrote:

On Sun, 16 Nov 2003 00:12:05 -0600, Pushkar Pradhan wrote:

I have a struct like this:
struct point {
int x;
int y;
};

Then I need to assign a certain point "=" another pt.
eg.
struct point p1, pArr[10];

/* initialize all pts. */
Now assign p1 to a certain element of pArr, this is how I did
and it works fine.
p1 = pArr[someIndex];

However, I just read my C book again and it says this stuff
must be done like this actually:
p1.x = parr[someIndex].x;
p1.y = parr[someIndex].y;

Please tell us the name of the C book so that we can all
avoid it.

Careful. Maybe he has misread the book. (This has happened
before in clc - someone has said "my book says <foo>" when in
fact it says <not foo>).

What you have done is fine.

Agreed.

He MAY have misread a section to do with detecting equality.
Statements such as:

if (p1 == pArr[ix]) {/* whatever */}

are not defined, and must be broken up into tests on the
individual components. Again, the name of the book would be
worthwhile.

--
Chuck F (cb********@yahoo.com) (cb********@worldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net> USE worldnet address!

[Pushkar Pradhan]

The book is:
The C Programming Language by KERNIGHAN & RICHIE.
Ok I don't think they explicitly said that, I just concluded it from
this code in the book:
/* addpoint: add two points */
struct point addpoint(struct point p1, struct point p2)
{
p1.x += p2.x;
p1.y += p2.y;
return p1;
}
My question is couldn't you just do:
p1 += p2;

Sheldon Simms wrote:

On Sun, 16 Nov 2003 00:12:05 -0600, Pushkar Pradhan wrote:

I have a struct like this:
struct point {
int x;
int y;
};

Then I need to assign a certain point "=" another pt.
eg.
struct point p1, pArr[10];

/* initialize all pts. */
Now assign p1 to a certain element of pArr, this is how I did and it
works fine.
p1 = pArr[someIndex];

However, I just read my C book again and it says this stuff must be done
like this actually:
p1.x = parr[someIndex].x;
p1.y = parr[someIndex].y;

Please tell us the name of the C book so that we can all avoid it.
What you have done is fine.

[Joona I Palaste]

Pushkar Pradhan <pu*****@gri.msstate.edu> scribbled the following:

The book is:
The C Programming Language by KERNIGHAN & RICHIE.
Ok I don't think they explicitly said that, I just concluded it from
this code in the book:
/* addpoint: add two points */
struct point addpoint(struct point p1, struct point p2)
{
p1.x += p2.x;
p1.y += p2.y;
return p1;
}
My question is couldn't you just do:
p1 += p2;

This is because += is different than =. Simple assignment (with =) is
always defined for structures. "Plus assignment" (with +=) is not. For
example, if you had this structure:
struct namedpoint {
char *name;
int x;
int y;
};
how would the compiler treat "plus assignment" with those structures?

I hope this answers your question. If it doesn't, I'll provide more
detail, unless a real C guru does it first.

--
/-- Joona Palaste (pa*****@cc.helsinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"C++ looks like line noise."
- Fred L. Baube III