A basic syntax question

Hey,

I am just getting started with c++ and I am adjusting from php, which has proved difficult so far. Variable types are throwing me off.

I can't find anywhere how you would 'combine' two integers. For example:

int x = 5;
int y = 2;

and I want to make them 52 or 25. In php you can just separate them with a period and they would append. Is it similar in C++ or will I have to write a math formula in a function to derive the desired number from two augments?

Thanks!
David

>> I have to write a math formula in a function to derive the desired number from two augments

That's the one.

*Curse words*

,but thanks.

Could you supply me with this formula?

thanks

You use a stringstream:

Code:

---

#include <iostream>
#include <sstream>

int main() {
        int x = 5, y = 2;

        std::stringstream s;

        // Convert 'x' and 'y' to strings and concatenate them
        s << x << y;

        // Get full string with str() method
        std::cout << "'" << s.str() << "'" << std::endl;
       
        return 0;
}

---

Awesome, I love you!

But one more thing. How can I convert it back into an integer.

Sorry, I feel like I should be looking this stuff up myself, but I'm not on my best game today.

you can use atoi()

Code:

---

int value = atoi(s.str().c_str());

---

Will you love me too? :) ;) :)

Code:

---

#include <iostream>
#include <sstream>

int main() {
        int x = 5, y = 2;

        std::stringstream s;

        // Convert 'x' and 'y' to strings and concatenate them
        s << x << y;

        // Get full string with str() method
        std::cout << "'" << s.str() << "'" << std::endl;

        int z;
        // Extract an integer
        s >> z;
        std::cout << z << std::endl;
       
        return 0;
}

---

More info: http://www.cplusplus.com/ref/iostream/stringstream/

Thanks, and I love you too Mario :p.

It all works now, just seems like it took a lot to do something so small.

Bump because you mightn't have seen my reply.

This "something small" is not exactly something you commonly need. Usually what you do with numbers is add them, subtract them, divide them and so on. These things are easy to do in C++.
Concatenating numbers is not something you do often. You do that with strings. With strings, concatenation is easy: just use the + operator.
So to achieve what you want, you have to convert the numbers to strings, concatenate them, then convert the resulting strings back to a number.

It's the same in PHP, by the way, except that, due to PHP's weak typing, these conversions are implicit. Try it out:

Code:

---

$a = 1;
$b = 2;
$c = $a . $b; // Implicitly convert the values of $a and $b to strings.
echo get_type($c); // Echos 'string'.
$b += $c; // Implicitely convert the value of $c to int.

---

Thanks for all the help guys, I am actually working with an array.

I would appreciate any help with this code, it crashes onces it gets to board[8][2], I guess its probably a memory problem.

Code:

---

#include <iostream>
#include <sstream>
using namespace std;

int main() {                                          //begin main program
  int x = 1, y = 1;                                  //declare x and y
  int board[8][8];                                  //declare array board
  while ( y < 9 ) {                                //loop 8 times for y
    while ( x < 9 ) {                              //loop 8 times for x
      std::stringstream c;
      c << y << x;                                //append the values of x and y
      int tc = atoi(c.str().c_str());          //convert the result to an integer
      board[y][x] = tc;                            //set the integer value into the array
      cout<< tc;                                      //print the integer value
      cout<<  "\n\n\n";
      x = x + 1;                                    //incriment to x
    }//end first loop
    x = 1;                                          //reset x to 1
    y = y + 1;                                    //incriment to y
  }                                                      //end second loop

cout<< board[1][1] << "\n";
cout<< board[8][8] << "\n";
cout<< board[2][1] << "\n";
cout<< board[3][2] << "\n";
cout<< board[1][6] << "\n";
cin.get();
return 0;
}

---

sorry if the comments are bothersome, but they help me learn.

Code:

---

y = y + 1;//incriment to y

---

This can be simplified to:

Code:

---

y++;

---

EDIT: Same for x.

Thanks manutd, do you have any idea why this program is crashing?

since you're using it as an integer, wouldnt it be easier to

Code:

---

board[x][y] = y*10 + x;

---

Arrays are 0-based, but you treat them as 1-based.

I have never really used while loops to build an array I think that might be where your problem is. Try using a for loop

Code:

---


for(int i =0; i<8; i++){
 for(int j =0; j<8; j++){
  array[i][j] = 0;
}
}

---

thats the syntax

the array goes from board[0][0] to board [7][7]
you went up to 8

Thank you CornedBee, that was the problem
edit: and howee.
I think I am done now, so thanks again for all the help with my dumb questions.

There are no dumb questions from those who try :D