C/C++ dynamic string array?

Thesniperofdeath · 03-07-2011, 08:07 PM

Can you create a dynamic string array and using calloc(),realloc()?
Like:

Code:

string* x;
x = (string) calloc(x,sizeof(string));

corp769 · 03-07-2011, 08:54 PM

I know for in C, it would be like so:

Code:

string *string1;
array=(string *) malloc(size*sizeof(string));

I know that is using malloc(), but should be almost the same for you. C++ will normally cast for you:

Code:

string *string1;
string1=new string[size]

Josh

Thesniperofdeath · 03-07-2011, 09:00 PM

Quote:

Originally Posted by corp769

I know that is using malloc(), but should be almost the same for you. C++ will normally cast for you:

Code:

string *string1;
string1=new string[size]

How would you resize then?.thanks.

corp769 · 03-07-2011, 09:21 PM

Check this link out:

http://www.cplusplus.com/forum/general/11111/

I got to get going, I'm about to get off of work. I will return once I get home.

Josh

Aquarius_Girl · 03-07-2011, 09:48 PM

But C++'s string is already re-sizable:

Code:

#include <iostream>
using namespace std;

int main ()
{
     string s;
     
     s.append ("abc");
     s.append ("def");
     s.append ("ghi");
     
     cout << s << "\n";
}

corp769 · 03-07-2011, 11:09 PM

Quote:

Originally Posted by Anisha Kaul

But C++'s string is already re-sizable:

Code:

#include <iostream>
using namespace std;

int main ()
{
     string s;
     
     s.append ("abc");
     s.append ("def");
     s.append ("ghi");
     
     cout << s << "\n";
}

Thanks Anisha, I keep thinking of C instead of C++

paulsm4 · 03-07-2011, 11:27 PM

Hi -

Code:

  // Wrong!
  string* x;
  x = (string) calloc(x,sizeof(string));

Code:

  /* Correct for C */
  char *s = (char *)malloc (4);
  strcpy (s, "ABC");
  s = realloc (s, 7);
  strcpy (s, "ABCDEF");

Code:

  // Correct for C++
  string s = "ABC";
  s.append ("DEF");

z1p · 03-08-2011, 04:20 PM

Quote:

Originally Posted by paulsm4

Hi -

Code:

  // Wrong!
  string* x;
  x = (string) calloc(x,sizeof(string));

Code:

  /* Correct for C */
  char *s = (char *)malloc (4);
  strcpy (s, "ABC");
  s = realloc (s, 7);
  strcpy (s, "ABCDEF");

Code:

  // Correct for C++
  string s = "ABC";
  s.append ("DEF");

I think this would be a a C++ version that is closer to the C version.

Code:

  // Correct for C++
  string s = "ABC";
  s = "ABCDEF";    // the string object will adjust its internal memory as needed

Dark_Helmet · 03-08-2011, 05:28 PM

Quote:

Originally Posted by Thesniperofdeath

How would you resize then?

Anisha has already pointed out that C++ strings can change size on-the-fly. However, I assume your question is not about the length of the individual strings, but the number of strings in the array itself.

The way I normally do it is to create a vector whenever I need an array. My approach is a little different from corp769. Instead of:

Code:

string *string1;
string1=new string[size]

I would probably do something like:

Code:

std::vector<string> stringArray;

...

stringArray.push_back("ABCDEF");
stringArray.push_back("GHIJKL");

...

stringArray.erase(stringArray.begin());

Of course, the erase() method can be used to remove any member of the array that you want as long as it's given the right arguments; you're not limited to erasing only the first element.

And you can access the individual strings just like a traditional array:

Code:

std::cout << stringArray[2] << std::endl;

EDIT:
I didn't read the link corp769 gave. So if this was covered in it, my mistake.

posixculprit · 03-09-2011, 03:06 AM

Hello. Just a little observation, if I may, even though it might be somewhat off-topic. Unless one really knows what one is doing and decides that it is absolutely necessary, it is not a good idea to use C standard library memory allocation functions (*alloc()) in C++ programs. For instance, unlike new, *alloc() functions do not call object constructors and unlike delete, free() does not call object destructors.