?
Solved

return an size unknown array

Posted on 2007-11-28
9
Medium Priority
?
215 Views
Last Modified: 2010-04-01
how do i store an array returned by a function?


the size of the array is determined by the function, so I don't know how big of an array to create before hand.


how do I stored it?

reception_array = return_array ()


0
Comment
Question by:Troudeloup
  • 3
  • 2
  • 2
  • +1
9 Comments
 
LVL 53

Accepted Solution

by:
Infinity08 earned 1000 total points
ID: 20367961
The easiest way is to allocate the array on the heap :

        int *fun() {
            int *array = new int[10];
            // fill array
            return array;
        }

and call like this :

        int *array = fun();
        // do something with the array
        delete [] array;
0
 

Author Comment

by:Troudeloup
ID: 20367977
why heap?

it's  a very small array i need, i think stack is enough.
0
 
LVL 46

Assisted Solution

by:Kent Olsen
Kent Olsen earned 480 total points
ID: 20367994
Hi Troudeloup,

You might look into some of the already available classes to do the size management for you.  There is a vector class, as well as several list classes such as TList.

TList is probably overkill for an array of integers, though.  vectors is probably the way to go.



Good Luck,
Kent
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
LVL 46

Assisted Solution

by:Kent Olsen
Kent Olsen earned 480 total points
ID: 20368003
Hi Troudeloup,

The stack is automatically managed space that is used to hold program created objects (like parameter lists).

The heap is for user created objects, like those generated with 'new', malloc(), etc.


Good Luck,
Kent
0
 
LVL 86

Assisted Solution

by:jkr
jkr earned 520 total points
ID: 20368014
In such a situation, a 'std::vector' will be eaier to handle, since it also holds information about the size and manages the storage issue transparently, i.e. you don't have to care about that. You can just use it like

#include <windows.h>
#include <iostream>
#include <vector>
#include <string.h>
using namespace std;

vector<HWND> vw; // array for HWND

BOOL CALLBACK EnumWindowsProc(HWND hwnd,LPARAM lParam)
{
      char buf [1024];
      GetWindowText(hwnd,buf,1024);

      if(!strstr(buf,(char*)lParam)) return true;

       vw.push_back(hwnd);

      return true;
}

void PrintVCector(vector<HWND>& vw)
{
      for (vector<HWND>::iterator i = vw.begin(); i != vw.end(); ++i)
      {
            cout << "HWND: " << *i << endl;
            ShowWindow(*i , SW_SHOWNORMAL);
            SetForegroundWindow(*i);
      }}

int main()
{
      EnumWindows(EnumWindowsProc,(LPARAM)"Editor");
     
      PrintVector(vw);

   return 0;
}
0
 
LVL 53

Assisted Solution

by:Infinity08
Infinity08 earned 1000 total points
ID: 20368016
>> why heap?
>> 
>> it's  a very small array i need, i think stack is enough.

You don't know the size of the array at compile time, and you have to return the array from the function. Those are two very good reasons to use the heap instead of the stack.


Kdo's suggestion of using a vector is even better !
0
 

Author Comment

by:Troudeloup
ID: 20368027
uh, it's just 5 or 6 elements of type hwnd.

i think using containers is really an overkill :)

0
 
LVL 86

Assisted Solution

by:jkr
jkr earned 520 total points
ID: 20368068
No, not really. They're always safer to use and you won't have to worry if the amount grows larger. The performance impact is minimal.
0
 
LVL 53

Assisted Solution

by:Infinity08
Infinity08 earned 1000 total points
ID: 20368071
>> uh, it's just 5 or 6 elements of type hwnd.
>> 
>> i think using containers is really an overkill :)

What do you really want to do ?

Using containers does not give that much overhead, and makes your life easier, assuming that the two assumptions from your question still stand : size is unknown at compile time, and the array has to be returned from a function.
0

Featured Post

Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Article by: SunnyDark
This article's goal is to present you with an easy to use XML wrapper for C++ and also present some interesting techniques that you might use with MS C++. The reason I built this class is to ease the pain of using XML files with C++, since there is…
Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
The goal of the video will be to teach the user the concept of local variables and scope. An example of a locally defined variable will be given as well as an explanation of what scope is in C++. The local variable and concept of scope will be relat…
The viewer will learn how to pass data into a function in C++. This is one step further in using functions. Instead of only printing text onto the console, the function will be able to perform calculations with argumentents given by the user.
Suggested Courses

850 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question