change the address of one element of int table?

[dopiotrko]

Is it possible to change the address of one element of int table?
My program would be much simpler, if the first element of the table
would be same as last one. I mean:
int *s;
s=(*int)malloc(sizeof(int)*10);
…..
and no mater what I would do to this table I want s[0]==s[9] to be
true.
How to do this?

dopiotrko

[Eric Sosman]

do*******@o2.pl wrote:

Is it possible to change the address of one element of int table?
My program would be much simpler, if the first element of the table
would be same as last one. I mean:
int *s;
s=(*int)malloc(sizeof(int)*10);

You mean `(int*)', and it would be even better to leave
it out altogether.

…..
and no mater what I would do to this table I want s[0]==s[9] to be
true.
How to do this?

There's no direct way: s[0] and s[9] are separate objects
and are able to hold different values. You'll need to exercise
some discipline of your own, such as

1) Whenever you store to either of them, store to the other
as well.

2) Instead of accessing s[i], access s[i % 9] (you can make
the array one place smaller in this case).

3) Don't access the elements of s[] directly, but always
through an array of pointers `int *sp[10]' which has
been initialized so sp[0] = &s[0], sp[1] = &sp[1], ...,
sp[8] = &s[8], sp[9] = &s[0 /* not 9 */].

--
Eric Sosman
es*****@ieee-dot-org.invalid

[dopiotrko]

Thanks.
Very helpful
Especially last option.

dopiotrko

[dopiotrko]

Thanks.
Very helpful
Especially last option.

dopiotrko

[Ben Bacarisse]

do*******@o2.pl writes:

Thanks.
Very helpful
Especially last option.

I may also be worth considering a circular linked list. Once set up,
you can repeat:

use(list_ptr->value);
list_ptr = list_ptr->next;

as often as you like, cycling round the values.

--
Ben.

[Malcolm McLean]

<do*******@o2.plwrote in message news:

Very helpful
Especially last option.

Essentially you don't want an array, you want a wrapped buffer.

So maybe a structure and some macros

typedef struct
{
int *buff;
int capacity;
} CIRCULAR;

int getval(c, i) (c)->buff[(i)%(c)->capacity]

void putval(c, i, value) (c)->buff[(i)%(c)->capacity] = (value)

is the way to go.

--
Free games and programming goodies.
http://www.personal.leeds.ac.uk/~bgy1mm