resizable array of pointers

[David W]

Re: resizable array of pointers

"Mark" <mnbayazit@gmai l.comwrote in message
news:1160102057 .156398.52090@i 42g2000cwa.goog legroups.com...

David W wrote:

My guess is that the numbers you are putting in there no longer exist, but you didn't include

that

code. If the ints are ordinary local variables they may have gone out of scope. You may need to
create each int to be stored with 'new' if that's the case (and delete later).

>
okay, that worked like a charm!
>
now..last question..i hope.
>
i've got my destructor
>
ObStash::~ObSta sh()
{
delete [] storage;
}
>
but will that be sufficient to prevent leakage?

Not if the objects pointed to were created with 'new'.

since it's an array of pointers. i figure i would have to delete each
pointer first,

Yes, and to the correct type of pointer as well (the same type created with 'new').

and then delete the array, since it's declared as void
**storage, however.. i can't delete each pointer because they delete
void* is undefined!
>
but, from my understanding, it's not necessarily delete integers
anyways..

Yes it is.

they'll take care of themselves..

No they won't. If they were created with 'new' they consume space in the free store like anything
else until they are explicitly deleted.

but the Student class
however, is another story.

A related story.

class Student
{
string name;
ObStash scores;
>
public:
Student(string name);
void print();
void cleanUp();
};
>
the string has it's own destructor i believe, and should clean up after
it's self...

Yes, as part of the destruction of the Student.

the obstash's destructor should clean up the scores too i think..

No, it shouldn't. It can't know the types really being pointed to by the array elements, and it
can't know whether those objects were created with 'new'.

but what about when
>
ObStash students;
>
goes out of scope?
>
do i need to call the destructor for each object individually or
anything..? (delete each student manually)

Yes.

or..will they all die
gracefully?

No.

DW

[neel]

Re: resizable array of pointers


Mark wrote:

i need to make a class that can store anything (integers,objec ts,etc)
it needs to maintain a list of pointers to these objects
the list needs to be resized to accomodate more elements
i can't use any special classes
>
i just can't seem to figure it out.
>
i've got a pointer,
>
void *storage
>
which will point to the start of the list
>
then there will be one pointer, every 4 bytes (sizeof(void*))
>
which i *think* i can access by doing
>
storage[index*sizeof(vo id*)]
>
i'm not sure if I need to cast that to a void pointer or not, since
that's already what it's defined as...
>
but then to resize this beast, i'm completely lost
>
i create a new void pointer..
>
void* temp = new void*[length]
>
where length is the new size (how many pointers it will hold)
>
which should allocate length*4 bytes of memory...
>
and then i tried doing
>
for(int i=0; i<count; i++)
{
temp[i] = storage[i*size];
}
>
to copy the pointers over
where count is the number of elements currently in the stash, but my
compiler complains...
>
`void*' is not a pointer-to-object type
pointer of type `void *' used in arithmetic
>
and...i don't really know what else to do.
>
any help?

[neel]

link list


i have a single link list with with 5 nodes .if 5 nodes address part
pointing to 2nd node. then show there is a loop . code it in c.
help me.

[Victor Bazarov]

Re: link list

neel wrote:

i have a single link list with with 5 nodes .if 5 nodes address part
pointing to 2nd node. then show there is a loop . code it in c.

For C questions please ask in comp.lang.c. Also, read the FAQ before
posting (there and anywhere else). They won't do your homework just
like we won't.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Mark]

Re: resizable array of pointers


David W wrote:

"Mark" <mnbayazit@gmai l.comwrote in message
news:1160102057 .156398.52090@i 42g2000cwa.goog legroups.com...

David W wrote:

>
My guess is that the numbers you are putting in there no longer exist, but you didn't include

that

code. If the ints are ordinary local variables they may have gone out of scope. You may need to
create each int to be stored with 'new' if that's the case (and delete later).
>

okay, that worked like a charm!

now..last question..i hope.

i've got my destructor

ObStash::~ObSta sh()
{
delete [] storage;
}

but will that be sufficient to prevent leakage?

>
Not if the objects pointed to were created with 'new'.
>

since it's an array of pointers. i figure i would have to delete each
pointer first,

>
Yes, and to the correct type of pointer as well (the same type created with 'new').
>

and then delete the array, since it's declared as void
**storage, however.. i can't delete each pointer because they delete
void* is undefined!

but, from my understanding, it's not necessarily delete integers
anyways..

>
Yes it is.
>

they'll take care of themselves..

>
No they won't. If they were created with 'new' they consume space in the free store like anything
else until they are explicitly deleted.
>

but the Student class
however, is another story.

>
A related story.
>

class Student
{
string name;
ObStash scores;

public:
Student(string name);
void print();
void cleanUp();
};

the string has it's own destructor i believe, and should clean up after
it's self...

>
Yes, as part of the destruction of the Student.
>

the obstash's destructor should clean up the scores too i think..

>
No, it shouldn't. It can't know the types really being pointed to by the array elements, and it
can't know whether those objects were created with 'new'.
>

but what about when

ObStash students;

goes out of scope?

do i need to call the destructor for each object individually or
anything..? (delete each student manually)

>
Yes.
>

or..will they all die
gracefully?

>
No.
>
DW

hm.. I think I was getting confused with something else. thank you for
your help.