Memory Allocation

[Cancer Sol]

Today, I was learning about Memory Allocation, using new and delete.
However，when I made a test program, the value wasn't what I wanted it to be.

c++:

#include <iostream> using namespace std; int main() {     int number;     cin >> number;     int *ptr_number = new int[number];//I tried to assign *ptr_numbers the value of number     cout << *ptr_number;//The output wasn't what I entered though }

What did I do wrong there?

[Panphobia]

You just initialized a new array of integers of size number, you did not store the value of number in it.

[Cancer Sol]

Panphobia @ 4/4/2013, 5:03 pm wrote:

You just initialized a new array of integers of size number, you did not store the value of number in it.

Oh.. the example in the book is kinda confusing then :/

How do I assign it the value of what I input then?

[Panphobia]

use ( ) instead of [ ] and everything else the same

[Cancer Sol]

Panphobia @ 4/4/2013, 5:50 pm wrote:

use ( ) instead of [ ] and everything else the same

Thanks, it works now
What if I left it like that so it's an array, how do I assign it a value? Let's just say we'll assign it to [0]

[Panphobia]

you can use a for loop from 0 to the array length and add values to all indexes of the array

[Cancer Sol]

Oh wait, actually I think I know how to do it now.
Still not too sure, but I'll just try it out tomorrow.

[wtd]

Quick tip:

code:

#include <iostream> #include <algorithm> int main() {         int *foo = new int[10];         std::fill(foo, foo + 10, 0);         for (int i = 0; i < 10; i++)         {                 std::cout << foo[i] << std::endl;         }         return 0; }

[Insectoid]

wtd @ Fri Apr 05, 2013 1:08 am wrote:

Quick tip:

code:

#include <iostream> #include <algorithm> int main() {         int *foo = new int[10];         std::fill(foo, foo + 10, 0);         for (int i = 0; i < 10; i++)         {                 std::cout << foo[i] << std::endl;         }         return 0; }

Why didn't they ever teach me this in school? So many for loops I didn't have to write!

[wtd]

The STL (Standard Template Library) is not for the faint of heart. It makes deep use of templates, which are tricky, and do not result in pleasant error messages.

Teachers avoid it because C++ is complicated enough to teach as it is, but also because many employers who hire programmers to work in C++ also avoid it. To some extent that situation is a chicken and egg problem.

[Cancer Sol]

wtd @ 4/5/2013, 1:08 am wrote:

Quick tip:

code:

#include <iostream> #include <algorithm> int main() {         int *foo = new int[10];         std::fill(foo, foo + 10, 0);         for (int i = 0; i < 10; i++)         {                 std::cout << foo[i] << std::endl;         }         return 0; }

I saw that in my ebook already, thanks anyways
The example I saw didn't say it was for arrays, so I was kind of confused.

Btw, is there a way to delete a non-integer pointer? Since I can't do something like this:

c++:

POINT *cursorpos = new POINT[amount];

since it's not an enum or integer... is it even possible to get memory from the free store for the structure POINT?
Edit: Nevermind, reread it.. what does this do?

code:

std::fill(foo, foo + 10, 0);

and what does the algorithm header file allow me to do?

[nullptr]

Including <algorithm> lets you use a bunch of useful, generalized functions, like swapping, sorting, searching, etc. You can find a description of all these algorithms (including fill) at http://www.cplusplus.com/reference/algorithm/

[Cancer Sol]

I'm so stupid, I could've just googled that -_-
Thanks

[Cancer Sol]

wtd @ 4/5/2013, 4:43 pm wrote:

The STL (Standard Template Library) is not for the faint of heart. It makes deep use of templates, which are tricky, and do not result in pleasant error messages.

Teachers avoid it because C++ is complicated enough to teach as it is, but also because many employers who hire programmers to work in C++ also avoid it. To some extent that situation is a chicken and egg problem.

What do you mean by The STL is not for the faint of heart? like it's just really hard?
Should I even bother with it then?

[wtd]

The STL requires a reasonably deep knowledge of C++. Of course, trying to figure it out can be a good incentive to investigate the more interesting concepts in C++.