setprecision and floating point

Question

Running the following code I expect to receive such an output:

Desired output:
Car     Hours    Charge
1        1.5      2.00
2        4.0      2.50
3       24.0     10.00

But the results comes out as follows:

Actual output:
Car     Hours    Charge
1        2       2
2        4       2.5 
3    2e+01      10

Any suggestions that can guide me to use the correct floating point comparison and using setprecision correctly is welcome.

int main()
{
    double hour[3];
    double charge[3];

    double sum_hour = 0;
    double sum_charge = 0;

    for (int i = 0; i < 3; i++)
    {
        cout<<"Enter the hours for car No. "<<i<<": ";
        cin>>hour [i];

        if (hour [i] <= 3)
            {charge [i] = 2.00;}
        if (hour [i] > 3 && hour [i] < 24)
            {charge [i] = (2.00 + (ceil(hour [i] -3))*0.5);}
        if (hour [i] == 24)
            {charge [i] = 10.00;}

        sum_hour  = sum_hour + hour [i];
        sum_charge = sum_charge + charge [i];
    }

    cout<<"Car"<<setw(10)<<"Hours"<<setw(10)<<"Charge"<<endl;

    for (int i = 0; i < 3; i++)
    {
        cout<<i+1<<setw(10)<<setprecision(1)<<hour[i]<<setw(10)<<setprecision(2)<<charge[i]<<endl;
    }
    cout<<"TOTAL"<<setw(6)<<sum_hour<<setw(10)<<sum_charge<<endl;

}

I ran the code in codeblocks. I am just learning the adjustment of floating points and setprecision — SRYZDN, Jan 21 '15 at 12:39

score 6 · Accepted Answer · answered Jan 21 '15 at 12:41

6

std::setprecision by default sets the total number of significant digits that are shown (ie. including the ones before the decimal point).

To set the number of digits shown after the decimal point, use std::fixed :

std::cout << std::fixed << std::setprecision(2) << 24.0;

will display :

24.00

answered Jan 21 '15 at 12:41

Sander De Dycker

16,053
1
35
40

How can i back form fixed to standard output? – Hiperon43 Jan 21 '15 at 12:50
1

@user3895596 : you can use [`std::defaultfloat`](http://en.cppreference.com/w/cpp/io/manip/fixed), to go back to the default floating point formatting. – Sander De Dycker Jan 21 '15 at 12:52

Hiperon43 · Answer 2 · 2015-01-21T12:48:48.893

1

You need function fixed to make cout write digits when it got only '0'.

So use it like this:

cout << fixed;
cout<<i+1<<setw(10)<<setprecision(1)<<hour[i]<<setw(10)<<setprecision(2)<<charge[i]<<endl;

edited Jan 21 '15 at 12:48

answered Jan 21 '15 at 12:13

Hiperon43

215
1
6

setprecision and floating point

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