Wierd precision for std::cout

[none]

When I do:

#include <vector>
#include <iostream>

....

std::vector<float> vec;
vec.push_back(2.2);
vec.push_back(2.3);
std::cout << vec[0] << std::endl;
std::cout << vec[1] << std::endl;

I get:

2.2000000476837158203125
2.2999999523162841796875

what goes on with the precision? I have not specified std::setprecision anywhere. I compile and run
the code on Ubuntu 9.04.

 

[Victor Bazarov]

When I do:

#include <vector>
#include <iostream>

...

std::vector<float> vec;
vec.push_back(2.2);
vec.push_back(2.3);
std::cout << vec[0] << std::endl;
std::cout << vec[1] << std::endl;

I get:

2.2000000476837158203125
2.2999999523162841796875

what goes on with the precision? I have not specified std::setprecision
anywhere. I compile and run the code on Ubuntu 9.04.

Could it be that your library implementation somehow has 22 as the
default precision?... You can always interrogate what the current
precision is by outputting 'cout.precision()'...

V

 

[Johannes Bauer]

Am 17.05.2010 22:28, schrieb none:

std::vector<float> vec;
vec.push_back(2.2);
vec.push_back(2.3);
std::cout << vec[0] << std::endl;
std::cout << vec[1] << std::endl;

I get:

2.2000000476837158203125
2.2999999523162841796875

what goes on with the precision? I have not specified std::setprecision
anywhere. I compile and run the code on Ubuntu 9.04.

http://www.parashift.com/c++-faq-lite/newbie.html#faq-29.16

Regards,
Johannes

--

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[Victor Bazarov]

Am 17.05.2010 22:28, schrieb none:

std::vector<float> vec;
vec.push_back(2.2);
vec.push_back(2.3);
std::cout<< vec[0]<< std::endl;
std::cout<< vec[1]<< std::endl;

I get:

2.2000000476837158203125
2.2999999523162841796875

what goes on with the precision? I have not specified std::setprecision
anywhere. I compile and run the code on Ubuntu 9.04.

http://www.parashift.com/c++-faq-lite/newbie.html#faq-29.16

The OP was talking about the number of digits in the output, which the
Standard specifies as 6 *by default*. IOW, the output should be

2.200000
2.300000

(because we expect rounding to the sixth digit after the decimal delimeter).

V