strcat and a char

This is a discussion on strcat and a char within the C++ Programming forums, part of the General Programming Boards category; I am brand new and working through the tutorial. I know the following is probably a little messy, please excuse ...

  1. #1
    Zen Apprentice jjacobweston's Avatar
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    strcat and a char

    I am brand new and working through the tutorial. I know the following is probably a little messy, please excuse - I am learning the conventions.

    I am having trouble with the strcat function. I want the program to ask for one character at a time and then, when four are collected and stored in "password" to check it for validity. I know there are probably other problems but I keep getting the compiler error on the "strcat" line.. so, if you see the problem with the "strcat" and any other problem, as well as pointing out any problems in my approach, I would greatly appreciate it.

    Code:
    int main(){
        
        char a;
        char password[4];
        int x;
        int y = 0;
    
        while(y==0){
        
        for(x=0; x<4; x++){
                 
                 if(x==0){
                          cout << "Enter first pin: ";
                          }
                 else if(x==1){
                      cout << "Enter second pin: ";
                      }
                 else if(x==2){
                      cout<< "Enter third pin: ";}
                 else {
                      cout << "Enter fourth pin: ";}
                      }
        cin >> a;
        strcat(password, a); //I also tried "&a" - it compiled without error but the program was non-functional..
                                         
        if(password == "1066"){
                    cout << "You have done it. You have entered the 4 magic numbers.";
                    y++;}
        else if (strlen(password)<4){
             cout << "Please enter more." << endl;}
        else {
             cout << "You have entered the incorrect four numbers. You have failed.";
             cin.get();
             return 1;
             }
    }
    cin.get();
              }
    Last edited by jjacobweston; 05-09-2005 at 04:20 PM.

  2. #2
    Tropical Coder Darryl's Avatar
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    Instead of strcat, I would directly modify the char array with

    password[x]=a;

    but for future reference, strcat( destination, source), both destination and source must be NULL-Terminated

    also, you can't compare c-string/char arrays this way:
    if(password == "1066")

    you will need to use if(strcmp(password, "1066"))

    but then password again will need to be NULL-terminated so I would suggest:
    char password[5];
    password [4] = '\0';

    finally, if you switch to using std::strings instead it will save you a lot of this trouble. For instance, strcat would simply be
    password += a;
    and comparison would work like you have it
    if(password == "1066")
    Last edited by Darryl; 05-09-2005 at 03:06 PM.

  3. #3
    Zen Apprentice jjacobweston's Avatar
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    Perfect

    Thank you much - exactly what I was looking for.
    Last edited by jjacobweston; 05-09-2005 at 04:20 PM.

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