while i was trying to DELETE a pointer with delete[] operator, it displays an error, why?

[topaz condor]

void sort(float *board, int how_many)
{
for (int j = 0; j < how_many; j++)
{
for (int i = 0; i < how_many - 1; i++)
{
if (board[i] < board[i + 1])
{
float replace = board[i];
board[i] = board[i + 1];
board[i + 1] = replace;
}
}
}
}

int main()
{
srand(time(NULL));
int how_many;

std::cout << "How many random numbers?" << std::endl;
std::cin >> how_many;

float* board = new float[how_many];

for (int i = 0; i < how_many; i++)
{
    //std::cin >> board[i];
    board[i] = rand() % 100 + 1;
}

sort2(board,how_many);

std::cout << std::endl;

for (int i = 0; i < how_many; i++)
{
    std::cout << *board << std::endl;
    board++;
}
delete[] board;

}

[sonic moss]

When your question is answered use !solved to mark the question as resolved.

Remember to ask specific questions, provide necessary details, and reduce your question to its simplest form. For tips on how to ask a good question use !howto ask.

[noble olive]

What error?

[topaz condor]

@noble olive

i code in visual studio

[noble olive]

You have changed the board pointer.

[topaz condor]

so that now i cant delete it?

[plain zephyr]

!f

[sonic moss]

void sort(float* board, int how_many) {
  for (int j = 0; j < how_many; j++) {
    for (int i = 0; i < how_many - 1; i++) {
      if (board[i] < board[i + 1]) {
        float replace = board[i];
        board[i] = board[i + 1];
        board[i + 1] = replace;
      }
    }
  }
}

int main() {
  srand(time(NULL));
  int how_many;

  std::cout << "How many random numbers?" << std::endl;
  std::cin >> how_many;

  float* board = new float[how_many];

  for (int i = 0; i < how_many; i++) {
    // std::cin >> board[i];
    board[i] = rand() % 100 + 1;
  }

  sort2(board, how_many);

  std::cout << std::endl;

  for (int i = 0; i < how_many; i++) {
    std::cout << *board << std::endl;
    board++;
  }
  delete[] board;
}

ManaHakaPl

Formatted by stabilewespe

[noble olive]

You need to keep the original pointer value to delete.

[topaz condor]

aaa okay'

so

i cant make any operation on this pointer to delete it?

[plain zephyr]

learn to use std::vector<float> please

using new/delete like that is a terrible idea

[topaz condor]

okay

[noble olive]

You can make another variable to print your array while keeping the board variable intact.

[hollow wadi]

can you stop fetishizing STL for 5 minutes and let beginners learn how to manage a resource first, and then teach them proper raii?

[plain zephyr]

it should be the other way around

[hollow wadi]

"let's learn how to drive down the highway without first learning how to switch gears"

[plain zephyr]

"let's learn how to drive down the highway without first learning how to build a motor"

[noble olive]

Most cars have automatic gear switching now, checkmate.

[hollow wadi]

and yet... in courses to acquire a driver's license what do all the candidates use? Cars with manual gears.

[hollow wadi]

I advocate for skipping libstdc++ internals, you advocate for skipping C++ basics and jumping straight into blackbox stl containers.

oh and also tell me, tomorrow when we manage compilcated resources like database connections, how are you gonna use new when that is not how the resource is created?

or other complicated handles

[plain zephyr]

they aren't black boxes, they have a well-defined interface that is much easier to intuitively grasp than new/delete and associated pointer juggling

[noble olive]

And that's why most C++ teaching sucks.

But really it's not that good of an analogy anyway.

[hollow wadi]

where is the sort2 function? who redirected the board pointer?

[plain zephyr]

and also new/delete isn't taught correctly anyway, because it is almost always taught in a way that is simply wrong in the presence of exceptions

[hollow wadi]

when the lecturer knows nothing about exception safety when managing resource lifetime, yes they are wrongly taught, when the lecturer does know about exception safety, they are taught correctly. Due to job market reasons finding a non-idiot lecturer is hard. I had a skilled lecturer.

[hollow wadi]

if you know the interface, but you do not know the internal implementation, it is still a blackbox

[hollow wadi]

it is crucial to explain exactly why STL containers' destructors do handle resource cleanup when exceptions happen, and NOT just say "vectors are a good practice, do not question my authority, do as I say maggot or you will not graduate from my course."

[noble olive]

It should be explained, but the best time for that is later.

But really users of other languages don't even flippin' bother.

[hollow wadi]

mmmm, remember try-with-resources for a database connection in java? 😄

horrendous mess

[noble olive]

Not sure how that's related.

[hollow wadi]

hey, did you fix the crash?

[thorn verge]

I partially agree with kolio here, knowing how to manage memory is great, especially because after suffering with memory management so much you'll appreciate STL 10x more

[topaz condor]

Didnt test it yet

[topaz condor]

Yes i did

[hollow wadi]

🎉

[lofty rock]

Hey guy,what is the "cin" function mean

[noble olive]

It's a "character input" variable.

[distant gale]

A) Don't post in other people's threads. Either create your own or for such small questions you can just ask in #cpp-help-text
B) It's not cin, it's std::cin. This differentiation is important, because cin, for all we know, could just be a local variable in your code.
C) std::cin is not a function, it's a variable of type std::ostream. The reason why it allows you to print to the console when used like this: std::cin << something is because the << operator is overloaded like so:

std::ostream& operator<<(std::ostream& o, const type_of_something& something) { ... }
```and whenever you do `std::cin << something`, that function there is being ran, which then handles the output.