Help with fraction to decimal code in C++

[bing3121]

Hello,

The following C++ code is what I am trying to use in a fraction class to convert a fraction to a decimal. the num and den are both ints. When I make a call to the function (f1.decimal_value()), the return value is 0.

Can any one help with this problem?

double fraction::decimal_value()
    {
        double decimal_num=num;
        double decimal_den=den;
        double decimal=(decimal_num)/(decimal_den);
        return decimal;
    }

[sicarie]

Hello,

The following C++ code is what I am trying to use in a fraction class to convert a fraction to a decimal. the num and den are both ints. When I make a call to the function (f1.decimal_value()), the return value is 0.

Can any one help with this problem?

double fraction::decimal_value()
    {
        double decimal_num=num;
        double decimal_den=den;
        double decimal=(decimal_num)/(decimal_den);
        return decimal;
    }

You don't pass num and den to the function, I'm guessing they get initialized to something weird - did you try printing them out to see what values they had in the function?

Another option is that the compiler might be trying to 'optimize' your code, seeing that num and den are ints, and converting decimal_num and decimal_den to ints without telling you - you could try (if the above doesn't work) something like:

double decimal_num = num*1.0; // makes sure a double is put in decimal_num

[bing3121]

You don't pass num and den to the function, I'm guessing they get initialized to something weird - did you try printing them out to see what values they had in the function?

Another option is that the compiler might be trying to 'optimize' your code, seeing that num and den are ints, and converting decimal_num and decimal_den to ints without telling you - you could try (if the above doesn't work) something like:

double decimal_num = num*1.0; // makes sure a double is put in decimal_num

I think you were right. After printing num and den bo remain ints. I tried to use the *1.0 but no-joy. Is there another way to convert num and den to double or float just in that function?

Thanks in advance

[sicarie]

And they're being passed/accessed correctly? (You didn't say anything, so I'm just checking.)

[bing3121]

And they're being passed/accessed correctly? (You didn't say anything, so I'm just checking.)

Sorry, the function is being called correctly, but the num and den are remaining as ints. The answer that is given is 0. I am not sure how to check other then cout the decimal_num and decimal_den to the screen during the operation.

If I enter 2/3 the dispaly shows
2 // cout<decimal_num<< endl;
3 // cout <<decimal_den<<endl;
decimal vaule is 0.

[sicarie]

I know I'm beating a dead horse here, but please just try this for me:

double fraction::decimal_value()
{
    double decimal_num=num;
    cout << num << '\t' decimal_num << endl;
    double decimal_den=den;
    cout << den << '\t' << decimal_num << endl;
    double decimal=(decimal_num)/(decimal_den);
    cout << decimal << endl;
    return decimal;
}

[bing3121]

I know I'm beating a dead horse here, but please just try this for me:

double fraction::decimal_value()
{
    double decimal_num=num;
    cout << num << '\t' decimal_num << endl;
    double decimal_den=den;
    cout << den << '\t' << decimal_num << endl;
    double decimal=(decimal_num)/(decimal_den);
    cout << decimal << endl;
    return decimal;
}

No luck - I am getting an overloaded << error. But you are trying to display num and decimal_num after decimal_num= num?

I am knew to C++ code - not sure I understand.

[sicarie]

Ok, that answered my question. Your problem lies here:

double fraction::decimal_value()
 

You are violating a rule of 'scope'. The problem is that in your main, you call decimal_value(), so memory for this function is being created. However, when num and den are created, they are given space in this new decimal_value() memory space - they are not the same num and den that are in your main(). To get them to be the same, you need to pass num and den to the function.

double fraction::decimal_value(int num, int den)
 

This gives num and den values, and from your main you call

double return_value;
return_value = decimal_value(num, den);
 

That should help clear it up.

[bing3121]

I know I'm beating a dead horse here, but please just try this for me:

double fraction::decimal_value()
{
    double decimal_num=num;
    cout << num << '\t' decimal_num << endl;
    double decimal_den=den;
    cout << den << '\t' << decimal_num << endl;
    double decimal=(decimal_num)/(decimal_den);
    cout << decimal << endl;
    return decimal;
}

Hello,

disregard my last message.

display shows
3 3
4 4
after entering 3/4 fraction answeer = 0

[Ganon11]

When you are assigning decimal_num and decimal_den, try

decimal_num = static_cast<double>(num);
decimal_den = static_cast<double>(den);

to explicitly cast the ints to doubles.

[Coldfire]

while doing this

double decimal=(decimal_num)/(decimal_den);

"it is possible for a value like 0.123 to be converted to 0 depending upon the particular compiler"

In your case the double decimal value loses the imaginary part of the result. So, you need to store this result by typecasting it or using routines like atof(). Try using float. I dont have the compiler to test this simple thingy rightnow but try the above recommendations

[bing3121]

When you are assigning decimal_num and decimal_den, try

decimal_num = static_cast<double>(num);
decimal_den = static_cast<double>(den);

to explicitly cast the ints to doubles.

Hello,

using static_cast did not work. The function is part of a fraction class I made. Here is how I call it in the main:

case 'D': get_fraction(f1);
f1.decimal_value();
cout<<"the Decimal value is ==> " << f1 << endl; 
break;

the get_fraction() is a local function to the main.

f1 is a loacal variable of type fraction

[sicarie]

Hello,

using static_cast did not work. The function is part of a fraction class I made. Here is how I call it in the main:

case 'D': get_fraction(f1);
f1.decimal_value();
cout<<"the Decimal value is ==> " << f1 << endl; 
break;

the get_fraction() is a local function to the main.

f1 is a loacal variable of type int

f1 isn't a user-defined container of some sort (class, struct,...)? That would definitely be my guess as to why the precision is disappearing, but even then, you have some interesting implementations in this program...

[Coldfire]

Hello,

disregard my last message.

display shows
3 3
4 4
after entering 3/4 fraction answeer = 0

Problem Solved ...........you just need to do this
double decimal=(double)(decimal_num)/(decimal_den);
or
double decimal=(float)(decimal_num)/(decimal_den);

[sicarie]

Problem Solved ...........you just need to do this
double decimal=(double)(decimal_num)/(decimal_den);
or
double decimal=(float)(decimal_num)/(decimal_den);

And already a Problem Solver... nice!

[Coldfire]

And already a Problem Solver... nice!

:D

_____________________________

P.S. I am so sick of this message: The message you have entered is too short. Please lengthen your message to at least 10 characters.

[sicarie]

:D

_____________________________

P.S. I am so sick of this message: The message you have entered is too short. Please lengthen your message to at least 10 characters.

Yeah, one of the mods in the javascript forum found a way to bypass it, but I never got a chance to ask him how...

[bing3121]

Problem Solved ...........you just need to do this
double decimal=(double)(decimal_num)/(decimal_den);
or
double decimal=(float)(decimal_num)/(decimal_den);

Okay tried it. Now the return is the fraction I enter.

example:

3/4
the decimal value is 3/4.

float fraction::decimal_value()
    {
        float decimal_num=num;
        cout<< num <<decimal_num<<endl;
        float decimal_den=den;
        cout<< den <<decimal_den <<endl;
        float decimal=(float)(decimal_num)/(decimal_den);
        return decimal;
    }

[Coldfire]

Okay tried it. Now the return is the fraction I enter.

example:

3/4
the decimal value is 3/4.

u mean the required answer ...in your case = 0.75 !

[bing3121]

u mean the required answer ...in your case = 0.75 !

yes, that is correct. I have it working now. It is amazing that something so small can take so long make work when you are a newbie to c++

Thanks for the help