simple class programming but getting lost.

[Acidburn]

We've been told to design our own class for strings. I've sat down and managed everything so far but I've stumbled accorss something. We've been asked to implement a concat algo.

strings* strings::concat(strings *s)
{
	char str[10];

		for(int i=0; i<5;i++)
		{
		str[i]=m_psz[i];
		}

		for (int j = 0 ; j < 5 ; j++)
		{
		str[j+5] = strings.m_psz[j];
		}

	return s;
}

I've managed to write a main for it

s1 = new strings("hello");
	s2 = new strings("world");
	s3 = new strings("00000000000000000000000000000000000000000000000");
string *s3 = s1->concat(s2);

	s3->print();

	delete s1, s2,s3;

I know its imcompolete but its also driving me nuts.....any ideas?

[Dave Sinkula]

Quickie concatenation algorithm.

[Acidburn]

Quickie concatenation algorithm.

doesnt help much since im passing it 2 objects... I've got it working but I dont know how to pass the object back:

strings* strings::concat(strings *s)
{
	char str[10] = {0};
	cout << endl;

		for(int i=0; i<10;i++)
		{
			str[i]=m_psz[i];
		}
		cout << "Value of str array is: "<<str << endl;

		for (int j = 0 ; j < 5 ; j++)
		{
			cout<< s->m_psz[j];
			str[j+4] = s->m_psz[j];
		}
		cout << "After function the str value is: "<< str;

	return str;
}

only when I put return str it errors and moans at me.

s1 = new strings("hello");
	s2 = new strings("world");
	s3 = new strings("00000000000000000000000000000000000000000000000");

	
	s1->print();
	s2->print();
	
	

cout << "\n**Now calling the concat function **\n" <<endl;

s3 = s1->concat(s2);

	s3->print();

[Dave Sinkula]

Concatenation to me means adding text to an existing string. Apparently your version is to take two strings and create a new third string. But you aren't new ing the third string when you create it (from the two strings that will compose it).

[Acidburn]

Concatenation to me means adding text to an existing string. Apparently your version is to take two strings and create a new third string. But you aren't new ing the third string when you create it (from the two strings that will compose it).

well I've had a go at putting the new in :

s3 = new strings(NULL) ;
s3 = s1->concat(s2);

	s3->print();

delete s1, s2;

the question is:

...a useful method function could be the following one:

class Strings {

private :
..
..

public :
..
strings *concat (string *s);

};

The prupose of the concat method is to take the current object (on which the method is called) as well as the passed strings object and produce a new string object which consitist of joining those 2. An illustrating texting code for the method might look like:

strings *s1 = new string("Hello);
string *s2 = new string("World");

string s3 = s1->concat(s2);
s3->print();

delete s1, s2 ,s3;

the above code should print out HelloWorld

[Dave Sinkula]

Ah. Here was my messing with a setup.

#include <iostream>
#include <cstring>
#include <cstddef>

namespace my
{
   class string
   {
      char *text;
   public:
      string(const char *init = "")
      {
         std::size_t size = strlen(init);
         text = new char[size + 1];
         strcpy(text, init);
      }
      ~string()
      {
         delete[] text;
      }
      string &concat(const string &s)
      {
         std::size_t size = strlen(text) + strlen(s.text);
         char *temp = new char[size + 1];
         strcpy(temp, text);
         delete[] text;
         strcat(temp, s.text);
         text = temp;
      }
      friend std::ostream& operator<< (std::ostream &o, string &s);
   };

   std::ostream& operator<< (std::ostream &o, my::string &s)
   {
      return o << s.text;
   }
}

int main()
{
   my::string one("Hello"), two(" world");
   std::cout << one << '\n';
   std::cout << two << '\n';
   one.concat(two);
   std::cout << one << '\n';
   return 0;
}

/* my output
Hello
 world
Hello world
*/

There should be some of the general ideas you are looking for in there.

[edit]Some mods:

string *concat(const string &s)
      {
         std::size_t size = strlen(text) + strlen(s.text);
         char *result = new char[size + 1];
         strcpy(result, text);
         strcat(result, s.text);
         return new string(result);
      }

int main()
{
   my::string one("Hello"), two(" world"), *three = one.concat(two);
   std::cout << one << '\n';
   std::cout << two << '\n';
   std::cout << *three << '\n';
   return 0;
}

But my C++ sucks in this area, so I'm pretty sure it's missing correctness.