college needs help again...ya diggg

Does anyone see whats wrong with the code

Hey im back everyone
Really need some help or rather some hints
Last time i was stressing over something that was very simple .

Everyone on the site seems so nice and im loving it.

Need help ...i need help please pretty please

Code:

---



#include<iostream>
using namespace std;

int main(void)
{
    system("TITLE Calculator")

    char cChar;
    double dfirstnumber;
    double dsecondnumber;
    char cDoagain;
   
do
(
    system("CLS");
    cout <<"please enter the first number you would like to use"
        << endl;
    cin >> dfirstnumber;
    cout << " please enter the operation that you would liek to complete"
      << " (+,-,* or /)" << endl;
    cin >> cChar;
   
    cout << " please enter the second number you would like to use"
        << endl;
       
    switch (cChar)
    (
    case "+":
        cout << " The answer is " << dfirstnumber << " + " <<
                dsecondnumber << " * " << (dfirstnumber + dsecondnumber) << endl;
        break;       
    case "-"
        cout << " The answer is " << dfirstnumber <<  "-" <<
                dsecondnumber << " * " << (dfirstnumber - dsecondnumber) << endl;
        break;     
    case "*":
        cout << " The answer is " << dfirstnumber << " * " <<
                dsecondnumber << " * " << (dfirstnumber * dsecondnumber) << endl;
        break;
    case "x":
        cout << " The answer is " << dfirstnumber << " x " <<
                dsecondnumber << " * " << (dfirstnumber * dsecondnumber) << endl;
        break;       
    case "X":
        cout << " The answer is " << dfirstnumber << " X " <<
                dsecondnumber << " * " << (dfirstnumber = dsecondnumber) << endl;
        break;
   
    case "/":
        if (dsecondnumber==0)(
            cout << " That is an invalid operation" << endl;
            )else (
        cout << " The answer is " << dfirstnumber << " / " <<
                dsecondnumber << " * " << (dfirstnumber / dsecondnumber) <, endl;
                )
                break ;
               
    default:
      cout << " That is an invalid operation" << endl;
      break;
      (
     
      cout << " Would you like to statr again ? ( y or n ) "
      << endl
      cin >> cDoagain;
      )while( cDoagain == " Y " || cdoagain ==  "y");
      system (" PAUSE")
      return 0;
      }

---

despite you editing, I don't see a question anywhere. at least not a specific one.

There is A LOT wrong in that entire code, look through it again very carefully.

With a switch statement, you can only use integers, not characters. So, for the operators, try giving them a number value, having your users type that number to perform the operation, and then keep using that number. Or, another thing you could do is use if...then...else statements. I only took a quick glance at it though, so there may be other things wrong with your code, but that should help (I remember making the same mistake doing the same thing, so I recognized it easily).

Another quick fix

You can use a char with a switch statement, then just have to be enclosed in ' ' and not " "like

Code:

---

case 'a':
break;

case 'b':
break;

---

You can? Sorry then, perhaps I didn't single quote it then... lol, I don't remember, but anyway, to explain the "Another quick fix" post, that was supposed to be the beginning of an edit to my even earlier post, with some more help, but my computer started lagging and everything screwed up.

Ok im just gonna make a quick list of things i noticed. (my computer messed up too so i couldnt finish my edit of the other post)

1. using () where there should be

Code:

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{}

---

2. using " " where there should be ' '
3. missing ; in a couple places
4. missing cin>> for the dsecondnumber variable
5. poor indentation

thanks everyone i will keep fixing them......doing it right now

Code:

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int main(void)

---

should be :

Code:

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int main()

---

No. In C++, both methods are exactly equivalent. In C, it's different, but this is the C++ programming forum.

Actually, it should be

Code:

---

int main(int argc, char *argv[])

---

but let's not get picky.

int main() and int main(void) are both better than int main(int argc, char *argv[]) in this case. All are legal and standard, but the first two indicate that no command line arguments are being used.

Perhaps I should post the contents of a PM replying to laserlight.

Quote:

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Originally Posted by dwks

Quote:

---

Originally Posted by laserlight

Quote:

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Originally Posted by dwks

Actually, it should be

Code:

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int main(int argc, char *argv[])

---

but let's not get picky.

---

What is your reasoning for saying that command line parameters should be included even when the command line arguments are not used?

Regards,
laserlight

---

In C, int main() is preferred over int main(void), because the latter means that main takes no parameters, and the code generated for it sometimes assumes this; so when argc and argv are passed to the program by the operating system, the stack can get corrupted.

Or so I hear. Someone else (matsp, I think) explains it better than I.

Anyway, in C++, since int main() and int main(void) are exactly the same -- that is, zero parameters, not unknown parameters -- I thought that the same mechanism might be generated, assuming that no parameters were passed to main(). I don't actually have any proof for this line of reasoning, however.

Another way of putting it: I think the int main() C-style function declarations (with an unknown number of parameters) were dropped from C++ along with function prototypes, like this.

Code:

---

int fputc();

---

So it would seem that int main() became equivalent to int main(void), and since int main(void) is not completely proper, one shouldn't use either in C++.

Any feedback on this would be appreciated.

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I guess if int main(void) is okay then int main() is okay too.

I have never heard of that before, but I seriously doubt it is an issue any more. Also, since int main() is standard C++, you can safely use it on any standards conforming compiler.

You're also missing the header file for system() (even though VC++ automagically includes certain headers for you).

The only reason there would be stack corruption based on the parameters to main is if it's a "callee clean stack" function. In x86 that isn't the common case, although Windows __stdcall calling convention does that. However, main is not a __stdcall function, so it's the responsibility of the caller to clean up the stack.

Other architectures may vary of course, depending on what the functionality that different instructions offer. But C-code basicly requires caller-stack-cleanup because of the ability to take variable number of arguments - the called function may not know [from a static analysis standpoint] the number of arguments, so the clean-up will need to be in the calling code for these functions at the very least.

--
Mats

So even in C int main() is the same as int main(void)? Strange, I could have sworn that someone said they were different. Actually, I thought it was you. ;)

Here's the "int main()" vs. "int main(void)" thread.

http://cboard.cprogramming.com/showthread.php?t=88714

Edit: The only dispute is regarding the situation in C - in C++ they are definitely the same, since in C++ the absence of an argument in a function declaration means unambiguously that there aren't any.

Oh, it wasn't matsp. Sorry. Mistaken identity. :)

Quote:

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The only dispute is regarding the situation in C - in C++ they are definitely the same, since in C++ the absence of an argument in a function declaration means unambiguously that there aren't any.

---

I don't understand.

In C, int main() is okay, because it means that main()'s arguments are unknown, and when it's passed argc and argv, the code won't toast the stack because, not knowing if it would be passed arguments or not, it made allowances for being passed arguments; whereas int main(void) is not okay, because the code could assume that it's not being passed any arguments, and mess up the stack when it is passed argc and argv.

Am I right so far? brewbuck's post supports me, as far as I can tell.

Quote:

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Originally Posted by brewbuck

In case you're wondering... The reason you must not declare main(void) is because of parameter passing conventions. Under most ABI's, C parameters are evaluated and passed right-to-left, with the CALLER of the function being responsible for managing the stack. However it is conceivable that on some platform somewhere it is the CALLEE's responsibility to clean the stack.

The problem is, if the function is specifically declared to take a void argument list, the compiler (rightly) assumes that it will never be passed any arguments, so it will not produce the code necessary to fix the stack if arguments had been passed. Then, when the main(void) gets invoked, the C library DOES pass arguments (argc, argv), but main is not aware of this. So when main() returns, the stack becomes corrupt and things go wrong.

---

Okay. So when prototypes like int fputc() (that is, prototypes without parameters) were excluded from C++, int fputc() became the same as int fputc(void) -- that is, the function takes no arguments, rather than "this function takes an unknown number and type of arguments".

Wouldn't functions, such as main(), be the same way? int main() in C has suddenly become int main(void) in both C and C++. int main(void) is not good in C, so why should it be good in C++?

There must be a hole in my reasoning somewhere. Feel free to point it out. ;)

[edit] It's probably that empty-function-prototypes-are-the-same-as-empty-function-declarations thing. [/edit]

A quick glance through that thread indicates that int main() is not valid in C because the C99 standard says so.

The C++98 standard says int main() is valid, and so we're done. C++ obviously has different requirements that force implementations to make it work.

If you do a prototype for a C function in C++, you should use

Code:

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extern "C" int somefunction();

---

, which tells the compiler to use "classic C" prototype interpretation, rather than C++ interpretation.

Of course, it doesn't really matter if you use main() or main(void) in the case where the callee cleans up the stack - it's impossible for the callee to know how many arguments where passed - there is also

Code:

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int main(int argc, char **argv, char **envp);

---

, where three arguments are passed.

--
Mats

Okay, good to know. Sorry, everyone, for hijacking the thread and all that.

Quote:

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Originally Posted by Daved

A quick glance through that thread indicates that int main(void) is not valid in C because the C99 standard says so.

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The C99 standard explicitly mentions "int main(void)" but says nothing about "int main()".

http://c0x.coding-guidelines.com/5.1.2.2.1.html

Of course in C++ there's no need for "void" to indicate the absence of arguments. I think someone once called the use of "void" for this purpose an "abomination" that was only necessary because of the old-style K&R function declarations in C, which are not allowed in C99 or C++.

Quote:

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Originally Posted by robatino

Of course in C++ there's no need for "void" to indicate the absence of arguments. I think someone once called the use of "void" for this purpose an "abomination" that was only necessary because of the old-style K&R function declarations in C, which are not allowed in C99 or C++.

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Several people in fact.. most notably, Bjarne Stroustrup said this about (void) between function parenthesis.
http://www.parashift.com/c++-faq-lit....html#faq-29.4