Thread: Simple Problem I'm sure..

I went from C to C++, but I am sure that isn't the problem. Perhaps strcmp() cannot compare two char's?

Thanks!

Code:

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

using namespace std;

int main()
{
    string chain;
    string input;
    int done = 0;
    int compare;
    char YN;


    while (done==0)
        {
            cout << "Input next element in chain: " << endl;
            scanf("%s", input);
            chain = chain + input;

            cout << "Done? (Y/N) " << endl;
            scanf("%c", YN);

            if (compare = strcmp(YN,'Y') == 0)
                done = 1
        }

    cout << Chain << endl;

    return 0;
}

Did you look at the documentation for strcmp()? Are the parameters you are using C-strings?

If you are writing a C++ program why are you using the C-stdio functions? The C-stdio functions do not know anything about C++ std::strings so your scanf() on line 20 should fail horribly. You should be using C++ iostreams to read and write variables to the console in C++.


Jim

Changed the char to a string so it should be able to compare it.

I do not completely understand what you mean by the second paragraph though. I need <stdio.h> for the scanf(). I thought the header files were essentially the same. :/

Code:

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

using namespace std;

int main()
{
    string chain;
    string input;
    int done = 0;
    int compare;
    string YN;


    while (done==0)
        {
            cout << "Input next element in chain: " << endl;
            scanf("%s", input);
            chain = chain + input;

            cout << "Done? (Y/N) " << endl;
            scanf("%s", YN);

            if (strcmp(YN,"Y") == 0)
                done = 1;
        }

    cout << chain << endl;

    return 0;
}

Errors:

Code:

C:\CPP\ListC\main.cpp||In function 'int main()':|
C:\CPP\ListC\main.cpp|20|warning: cannot pass objects of non-POD type 'struct std::string' through '...'; call will abort at runtime|
C:\CPP\ListC\main.cpp|20|warning: format '%s' expects type 'char*', but argument 2 has type 'int'|
C:\CPP\ListC\main.cpp|24|warning: cannot pass objects of non-POD type 'struct std::string' through '...'; call will abort at runtime|
C:\CPP\ListC\main.cpp|24|warning: format '%s' expects type 'char*', but argument 2 has type 'int'|
C:\CPP\ListC\main.cpp|26|error: cannot convert 'std::string' to 'const char*' for argument '1' to 'int strcmp(const char*, const char*)'|
C:\CPP\ListC\main.cpp|13|warning: unused variable 'compare'|
||=== Build finished: 1 errors, 5 warnings ===|

hmm seems like I needed to use char* and not string....

only one problem, how to add them together in a string?

Maybe I should be more clear in what I want.

I want the program to ask for a list of elements that corresponds to how a molecule is, so I can get the resonance structures from them later. i.e. input "C" and "C" and you get two C's in a row the string chain would equal CC which would be outputted "C - C" which for chemistry people is actually C2H6 (Ethane). So right now is just the simple part before I make it more complex.

I read a whole C book, at the end of the book I realized I really should have been learning C++... I'll have to read another book of stuff I already know again, fun. BUt for now, I just want to program a little.

Thanks

nvm, that question was retarded...lol

still have a problem though, will post in a nother topic.