setprecision problem

[Wing]

Hello everyone,

I have the following code:

///////////////////////////////////////
double num;
num=1234567890;
num+=(1.0/3.0);

cout.setf(ios::fixed);
cout<<setprecision(10);


cout<<num<<endl;
///////////////////////////////////////

The output is 1234567890.3333332539. I am wondering why the floating
numbers are not all "3". Why "2539" appears in the output?

Can anyone help me to solve this problem? Thank for so much.

 

[Nate Barney]

Hello everyone,

I have the following code:

///////////////////////////////////////
double num;
num=1234567890;
num+=(1.0/3.0);

cout.setf(ios::fixed);
cout<<setprecision(10);


cout<<num<<endl;
///////////////////////////////////////

The output is 1234567890.3333332539. I am wondering why the floating
numbers are not all "3". Why "2539" appears in the output?

Can anyone help me to solve this problem? Thank for so much.

This is a FAQ. See
http://www.parashift.com/c++-faq-lite/newbie.html#faq-29.16

Nate

 

[Spoon]

///////////////////////////////////////
double num;
num=1234567890;
num+=(1.0/3.0);

cout.setf(ios::fixed);
cout<<setprecision(10);


cout<<num<<endl;
///////////////////////////////////////

The output is 1234567890.3333332539. I am wondering why the floating
numbers are not all "3". Why "2539" appears in the output?

http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems

http://docs.sun.com/source/806-3568/ncg_goldberg.html