Fraction class

[wtd]

When dealing with numbers, it's not uncommon for us to use floating point numbers. The problem, however, is that floating point numbers are inherently inaccurate. The solution? Create a fraction class that stores the numerator and denominator separately, and overloads a number of operators and functions so that fractions can be dealt with much the same as other numbers.

Consider a simple example:

code:

#include <iostream> #include "Fraction.h" int main() {    Fraction a(1, 3), b(1, 2);    std::cout << a + b << std::endl;    return 0; }

[cimnik029]

does it reduce?

[wtd]

If I recall, there's a "simplify" function in there, yes.

[jamonathin]

I'm totally new to this, and the only thing I've understood so far is the "Hello World" program, but why can't i run anything, not even this program, it says Source File Not Compiled. So then I go to compile it, and att he bottom it says:
[Linker error] undefined reference to `WinMain@16'
ld returned 1 exit status
( I'm using Dev-C++ )

[Martin]

What are you using to try to run it?

[jamonathin]

I'm using CTRL+F9 to compile, and CTRL+F10 to run.

[Martin]

I mean, what program are you using? Visual Studio?

If so, you should run the program with F5, or click Debug -> Start

[jamonathin]

Dev-C++ 4.9.9.2, it's all I could find at the moment for free.

[Martin]

Okay, well, it seems like you're building it correctly.

Does the DOS window just pop up and disappear? If so, everything went correctly and your program just finished its execution. Add the following line to the end of your code to make it wait for your input before it exits (above the return 0; below everything else):

code:

int buff; cin >> buff;

[jamonathin]

Well, when I try this program, it says it must be compiled, so I compile it, and then I think it's done, I go to run it, and it says it must be compiled, and those error message I wrote earlier pop up.
When I try this:

code:

#include <iostream> using namespace std; void main() {      cout << "Hello World!\n"; }

it says

Quote:

5 \\KCI-FS\travmacv\CPU Science - C++\- Open Here.cpp `main' must return `int'

[Martin]

Ooh, good!

main is a function. In C++, there are no procedures, instead, everything must return a value. If you don't want something to return a value, you have it return void.

Your main function is the entry point to your code: that is, when your program is run, main is the first thing that is called.

void main is technically acceptable, but it's considered to be very bad coding. Instead of void main, use int main. At the end of it, you'll want to make it 'return 0;' which basically tells the OS that everything went okay.

[jamonathin]

ahh ok, thanks, ( took me a couple tries ). But now when I put the

code:

int buff; cin >> buff;

before the last }, it doesn't hold up for me, or say Hello world.
[ I feel like such a newb ]

[Martin]

code:

#include <iostream> using namespace std; int main () {      cout << "Hello World\n!";      int buff;      cin >> buff;      return 0; }

[jamonathin]

you're a bloody genious thanks for your help martin.

[Martin]

No problem. One thing that always confused me when I started learning C++ was the use of the line 'using namespace std;'

C++ has literally thousands of various functions, and, should you use a bunch of libraries, conflicts are going to occur when functions have the same name. 'using namespace std;' says 'use the standard (std) namespace'

A namespace is used to battle the problem of conflicting names. With namespaces, functions belong to a collection; in the above case, they belong to the 'std' collection.

The above code that I posted is the exact equivalent of this, without namespaces:

code:

#include <iostream> int main () {      std::cout << "Hello World\n!";      int buff;      std::cin >> buff;      return 0; }

Note the std:: at the beginning of the function. This says 'use std's cout function.'

The line 'using namespace std;' says 'whenever a function's not defined by the code, check to see if it's defined in std'

Now I suggest we leave wtd's fraction class topic alone. Make a new topic if you need more help.