String incorrect for output command target

[DarkAlex]

Ok, I'm back, and I have a new question. What am I doing wrong in this code?

int save()
{
    char * filename;
    char * fileext = ".rpg";
    cout<<"Save game?\n";
    cin>>choice;
    if (choice=="yes" || choice=="y" || choice=="Y" || choice=="Yes" || choice=="yES" || choice=="YES" || choice=="YeS" || choice=="yEs" || choice=="YEs" || choice=="yeS")
    {
                      cout<<"Save filename?\n";
                      cin>>filename;
                      filename=filename+fileext;
                      std::ofstream output(filename);
                      output <<startpoint<<' '<<yourname<<' '<<hp<<' '<<weapon<<' '<<attack<<' '<<maxhp<<' '<<gold<<' '<<frags<<' '<<dmg<<' '<<block<<' '<<bow<<' '<<handgrenade<<' '<<broom<<' '<<rope<<' '<<grapple<<' '<<stairboots<<' '<<goldplate<<' '<<goldgoblet<<' '<<goldbowl<<' '<<goldflatware<<' '<<rockbuster<<' '<<bluessword<<' '<<smsand<<' '<<lgsand<<' '<<bacon<<' '<<rbeef<<' '<<bbqpork<<' '<<bbqbeef<<' '<<chicken<<' '<<steak<<' '<<apple<<' '<<pear<<' '<<plum<<' '<<pineapple<<' '<<peach<<' '<<papaya<<' '<<cheese<<' '<<candy<<' '<<beaten<<' '<<broomequip<<' '<<rockbusterequip<<' '<<bluesswordequip<<' '<<bowgive<<' '<<taken<<' '<<computer<<' '<<motherboard<<' '<<floppydrive<<' '<<harddisk<<' '<<compucase<<' '<<os<<' '<<rps<<' '<<calculate<<std::endl;
                      output.close();
                      cout<<"Game Saved.\n";
    }
    else
    {
    }
    system("pause");
}

It gives me an error about using the wrong data type. What am I doing wrong and how can I fix it?

[Kernel Sanders]

Which line is giving you that error

[brewbuck]

If you want your input to be treated in a case-insensitive way, then do it. Checking to see if the input is equal to "yeS" is dumb. Nobody will ever type that. Seriously.

[DarkAlex]

Wait, i forgot that that was a modified version. For that code, the problematic line is:

filename=filename+fileext;

The real form of the code is this, and the erroneous line is bold:

int save()
{
    string filename;
    cout<<"Save game?\n";
    cin>>choice;
    if (choice=="yes" || choice=="y" || choice=="Y" || choice=="Yes" || choice=="yES" || choice=="YES" || choice=="YeS" || choice=="yEs" || choice=="YEs" || choice=="yeS")
    {
                      cout<<"Save filename?\n";
                      cin>>filename;
                      filename=filename+".rpg";
                      std::ofstream output(filename);
                      output <<startpoint<<' '<<yourname<<' '<<hp<<' '<<weapon<<' '<<attack<<' '<<maxhp<<' '<<gold<<' '<<frags<<' '<<dmg<<' '<<block<<' '<<bow<<' '<<handgrenade<<' '<<broom<<' '<<rope<<' '<<grapple<<' '<<stairboots<<' '<<goldplate<<' '<<goldgoblet<<' '<<goldbowl<<' '<<goldflatware<<' '<<rockbuster<<' '<<bluessword<<' '<<smsand<<' '<<lgsand<<' '<<bacon<<' '<<rbeef<<' '<<bbqpork<<' '<<bbqbeef<<' '<<chicken<<' '<<steak<<' '<<apple<<' '<<pear<<' '<<plum<<' '<<pineapple<<' '<<peach<<' '<<papaya<<' '<<cheese<<' '<<candy<<' '<<beaten<<' '<<broomequip<<' '<<rockbusterequip<<' '<<bluesswordequip<<' '<<bowgive<<' '<<taken<<' '<<computer<<' '<<motherboard<<' '<<floppydrive<<' '<<harddisk<<' '<<compucase<<' '<<os<<' '<<rps<<' '<<calculate<<std::endl;
                      output.close();
                      cout<<"Game Saved.\n";
    }
    else
    {
    }
    system("pause");
}

[Kernel Sanders]

ofstream's constructor can take a char * (a C string), not a C++ string

std::ofstream output(filename.c_str);

[matsp]

std::ofstream output(filename.c_str);

Or more correctly:

std::ofstream output(filename.c_str());

I would ask the "Save ?" this way:

do {
    cout<<"Save game?\n";
    cin>>choice;
} while (toupper(choice[0]) != 'Y' && toupper(choice[0]) != 'N');
if (toupper(choice[0] == 'Y')
   ... do saving.

Now that will of course accept "Yeah", "Yo" or "yn" as "Yes", but I think that's acceptable. If you do not want to do that, then you probably should write a proper parser that takes a list of valid "commands" for a particular situation, and only returns when you get a valid one.

--
Mats

[DarkAlex]

That helps, so I'll upgrade my games to do that. But how do I convert the string to a char? Or, in the first code I posted, append the extension to the filename?

[Kernel Sanders]

Append with the += operator and convert it to a C string char * with the c_str() function

[rags_to_riches]

As soon as you've formed an opinion, you're already wrong

Holy crap, how did my wife get a Sr. SWE job???

[DarkAlex]

Off topic, man...

What is the syntax for the c_str() function?

[Kernel Sanders]

Off topic, man...

What is the syntax for the c_str() function?

string s("whatever");
char *cs = s.c_str();

Google is your friend

[Daved]

char *cs = s.c_str();

should of course be:

const char *cs = s.c_str();

although you usually just pass it directly to the fstream function (or whatever legacy code requires the C style string).

[Kernel Sanders]

char *cs = s.c_str();

should of course be:

const char *cs = s.c_str();

although you usually just pass it directly to the fstream function (or whatever legacy code requires the C style string).

Off topic - can you recommend a good reference for C++'s const keyword? As a C programmer learning C++ const is one of my stumbling blocks

[Daved]

Maybe this: http://www.parashift.com/c++-faq-lit...rrectness.html

Otherwise, just the recommended books.

You might also try searching gotw and/or comp.lang.c++.moderated, although it might be difficult given that const can be used in many scenarios without actually explaining it.

[DarkAlex]

It keeps giving me errors...

int save()
{
    string filenameo;
    char * filename;
    do
    {
       cout<<"Save game?\n";
       cin>>choice;
    } while (toupper(choice[0]) != 'Y' && toupper(choice[0]) != 'N');
    if (toupper(choice[0] == 'Y'))
    {
                      cout<<"Save filename?\n";
                      cin>>filenameo;
                      filename=filenameo.c_str();
                      filename=filename+="rpg";
                      std::ofstream output(filename);
                      output <<startpoint<<' '<<yourname<<' '<<hp<<' '<<weapon<<' '<<attack<<' '<<maxhp<<' '<<gold<<' '<<frags<<' '<<dmg<<' '<<block<<' '<<bow<<' '<<handgrenade<<' '<<broom<<' '<<rope<<' '<<grapple<<' '<<stairboots<<' '<<goldplate<<' '<<goldgoblet<<' '<<goldbowl<<' '<<goldflatware<<' '<<rockbuster<<' '<<bluessword<<' '<<smsand<<' '<<lgsand<<' '<<bacon<<' '<<rbeef<<' '<<bbqpork<<' '<<bbqbeef<<' '<<chicken<<' '<<steak<<' '<<apple<<' '<<pear<<' '<<plum<<' '<<pineapple<<' '<<peach<<' '<<papaya<<' '<<cheese<<' '<<candy<<' '<<beaten<<' '<<broomequip<<' '<<rockbusterequip<<' '<<bluesswordequip<<' '<<bowgive<<' '<<taken<<' '<<computer<<' '<<motherboard<<' '<<floppydrive<<' '<<harddisk<<' '<<compucase<<' '<<os<<' '<<rps<<' '<<calculate<<std::endl;
                      output.close();
                      cout<<"Game Saved.\n";
    }
    else
    {
    }
    system("pause");
}

Erroneous lines are bold, and errors are:

In function `int save()':
508 invalid conversion from `const char*' to `char*'
509 invalid operands of types `char*' and `const char[4]' to binary `operator+'
509 in evaluation of `operator+=(char*, const char[4])'