C++ newb :D

[dez_666]

Hi im like just learning C++ and i decided to take a big leap by going from knowing how to use cout to making command line parameters.

So i tried this..

#include <cstdlib>
#include <iostream>

/*  int Add (char x,char y)
	{
	 		return(x+y);
}

*/

int main(int argc, int argv[])

{
 	
 	using std::cout;
 	using std::endl;
 	
    cout << argv[0]+argv[1] << endl;
}

And yes, the commented part was going to be a function but i couldnt get it to work so i just commented it for later experimentation. So when i run this by typing in "adder.exe 1 2"
i get an output of "8013972". can someone tell me what im doing wrong?
its probably something stupid that i missed.

 

[dez_666]

anyone wanna help me :3

 

[Shadow2531]

Can't test this at the moment, but try:

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

int cstringToInt(const char* s) {
    istringstream str(s);
    int i;
    str >> i;
    return i;
}

int main(int argc, char* argv[]) {
    if (argc != 3) {
        cout << "Usage: this.exe int1 int2" << endl;
        return EXIT_FAILURE;
    }
    cout << cstringToInt(argv[1]) + cstringToInt(argv[2]) << endl;
}

 

[dez_666]

it works.

but can you explain to me how to turn cmd line parameters into integers (so they can be added n stuff)?

 

[Shadow2531]

char* argv[] represents an array of C-style strings

If you run:
test.exe 1 2

argv[0] will be "test.exe".
argv[1] will be "1".
argv[2] will be "2".

argc represents the size of the array. In this case, it's 3.

So, to add 1 + 2, you need to convert "1" to 1 and "2" to 2. cstringToInt is one way to do that.

cstringToInt uses istringstream to do the conversion. You start off by contructing the stream to have a value of the C-style string you're passing to the cstringToInt (argv[1] and argv[2] in this case). Then, you create an int and do str >> i to grab the input from the string and dump it to the int. When you do this, it knows how to handle the conversion (in basically the same way cin >> i does).

However, instead of cstringToInt, you can use atoi(argv[1]) and atoi(argv[2]) if you want. They do about the same thing. See http://www.cppreference.com/stdstring/atoi.html

 

[WARnux]

Your avatar is quite distracting. Can you decrease the flashing?

 

[dez_666]

hmm. would you rather have it be text color RGB 0,0,0 and background color Hex 000000?

 

[ferrija1]

hmm. would you rather have it be text color RGB 0,0,0 and background color Hex 000000?

You don't have to do that, you could make the text #FFFFFF.

 

[WARnux]

Good one! No, 666 does not scare me because I know where it comes from.

 

[dez_666]

i didnt ask if it scared you and im sorry but i dont care