Comparing strings - beginner question

So I've just started out programming more or less and have run into trouble. I'm going through the c++ tutorial on the site and so far doing pretty well I believe. I've tried searching about the web for a reason for the problem stated below, but have come up empty handed - mainly I suspect because of an inability to phrase my question right as my programming vocabulary I still sadly lacking.

I'll work around the problem for now, but this is the first thing I just plain don't understand - and I'd like to. Any help is greatly appreciated.

Why does this work;

Code:

#include <iostream>
#include <cstring>


using namespace std;


int main()
{
    char a[2], c[2], b[2], asdf = 'A';


    if (strcmp (a, c) + strcmp (a, c) == 2) {
        cout << "They're all the same.";
        cin.get();


    }


    else {
        cout << "They're not the same. Silly C++ - they actually are.";
        cin.get();
    }


}

While this returns error "array must be initialised with brace-enclosed initializor"?

Code:

#include <iostream>
#include <cstring>


using namespace std;


int main()
{
    char a[2], c[2], b[2] = 'A';


    if (strcmp (a, c) + strcmp (a, c) == 2) {
        cout << "They're all the same.";
        cin.get();


    }


    else {
        cout << "They're not the same. Silly C++ - they actually are.";
        cin.get();
    }


}

Note all I've done is remove the not-used asdf variable. I really don't get this, but I'll work around it in the cmd Tic Tac Toe program I'm trying to create.


Thanks a lot for your time - I hope I'm not unknowingly breaking any forum rules, but if I am I'd like help in keeping with them as well. The site so far has been by far the best resource for learning for me a complete beginner. Thanks!


EDIT; The above is just a test-program for me to try out theories and principles in. It's not part of the actual program I'm trying to create - merely me trying to understand a concept.

Originally Posted by Yasha

While this returns error "array must be initialised with brace-enclosed initializor"?

Because you are trying to initialise b, which is an array of 2 char, as if it were a single char. You probably wanted to use a string literal like "A" instead.

By the way, this is bad:

Code:

strcmp (a, c) + strcmp (a, c) == 2

strcmp will return a positive integer if a is greater than c, but that integer does not have to be 1. (Also, you're just repeating strcmp(a, c) anyway.)

I see. I should probably just get some sleep if I'm making mistakes as simple this. I'd just really love to have this finished - I guess you know what that's like Thanks for the input. The goal for me is trying to find a way to identify when a player has got three in a row. The methods I've tried either result in nothing happening or whoever finishes a sequence involving either X or O's or a mix thereof get's credit. It's anonnoying the hell out of me - enough that I think it might be too advanced and that I should return to this later. I know finishing this would make my software-engineer-dad extremely proud though (as I work in a completely unrelated field).This was posted as a solution to a similar issue;


This was posted as an answer to a similar issue;

Code:

#include <iostream.h>

int main()

{
    char aline[125];
    char sline[125];
    char lbracket[2] = {"["};
    char rbracket[2] = {"]"};

     cout<<"Type in aline"<<endl;
     cin>>aline;

     if (aline[0]==lbracket[0])
     {
         cout<<"The first character was indeed a: [ "<<endl;
     }
     else
     {
         cout<<"The first character was not a: [ "<<endl;
     }    

         int stop;
         cin>>stop;    
 }

Why is this not comparable to;

Code:

#include <iostream>#include <cstring>


using namespace std;


int main()
{
    char a[2], c[2], b[2] = {"A"};


    if (a[0] == b[0]) {
        cout << "They're all the same.";
        cin.get();


    }


    else {
        cout << "They're not the same. Silly C++ - they actually are.";
        cin.get();
    }


}

Which for me does not work. It displays the else-message.

I apparently and sadly do not understand strings at all :/


Defining each char seperately made it work. Why - I do not understand.

Originally Posted by Yasha

Which for me does not work. It displays the else-message.

Because null terminated strings should be compared by using strcmp (or strncmp), not operator==. If you want the more "natural" operator== syntax, use std::string instead of null terminated strings.

So I think I got around the problem with the code below which should allow me to compare the three. It seems to work. Basing my 'real' program on this. It's correct, no?

Code:

#include <iostream>
#include <cstring>


using namespace std;


int main()
{
    char a[2] = {"A"};
    char c[2] = {"A"};
    char b[2] = {"A"};


//Display variables defined above just to be certain what they are.
    cout << a << b << c << endl;
//Again for clarification to myself displaying result of equation used below. 
    cout << (a[0] == b[0]) << endl;


    if (a[0] == b[0] && a[0] == c[0]) {
        cout << "They're all the same.";
        cin.get();


    }


    else {
        cout << "They're not the same. Silly C++ - they actually are.";
        cin.get();
    }


}

This:

Code:

char a[2] = {"A"};
char c[2] = {"A"};
char b[2] = {"A"};

should be:

Code:

char a[2] = "A";
char c[2] = "A";
char b[2] = "A";

Originally Posted by laserlight

This:

Code:

char a[2] = {"A"};
char c[2] = {"A"};
char b[2] = {"A"};

should be:

Code:

char a[2] = "A";
char c[2] = "A";
char b[2] = "A";

I tried it and it works too. But what's the difference? When should I use the curly brackets? EDIT; When writing to an array?


Also - should I upload the code for the finalized Tic Tac Toe for anyone interested in what I'm using this for?