Boost Users :
Subject: Re: [Boost-users] [test] CLOSE and CLOSE_FRACTION tolerance
From: Edward Diener (eldiener_at_[hidden])
Date: 2011-06-03 09:25:47
On 6/3/2011 8:45 AM, Edward Diener wrote:
> 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
>> |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 !
Or perhaps you mean that for both CLOSE and CLOSE_FRACTION both cases
above are calculated ? In which case I still do not understand what is
the difference between "percentage units" and "fraction of absolute value".
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