Re: [Boost-users] [test] CLOSE and CLOSE_FRACTION tolerance

Subject: Re: [Boost-users] [test] CLOSE and CLOSE_FRACTION tolerance
From: Edward Diener (eldiener_at_[hidden])
Date: 2011-06-03 08:45:59

On 6/3/2011 1:55 AM, Gennadiy Rozental wrote:
> Edward Diener<eldiener<at>  tropicsoft.com>  writes:
>
>>
>> I am trying to understand the tolerance value passed as the last
>> parameter to the BOOST_XXX_CLOSE and BOOST_XXX_CLOSE_FRACTION macros.
>> The doc says that for the former the value is percentage units while for
>> the latter it is the fraction of absolute values being compared. But in
>> each case there are two values, not just one. Which of the two values
>> are used to determine the tolerance amount in each case ? If both values
>> are being used in each case, how is the tolerance amount computed from
>> the tolerance value passed ?
>
> These are using strict check:
>
> |a-b|/|a|<  tolerance
> and
> |a-b|/|b|<  tolerance
>
> You can get weak check if you want (or instead of and above) by using
> close_at_tolerance predicate directly.

As I understand your answer, the first case above above refers to CLOSE 
and the second case above to CLOSE_FRACTION. Can you add that to the 
docs of both so that everyone can better understand it ? Thanks !