id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
5758	Boost.Test Floating-point comparison diagnostic output does not support radix 10	Paul A. Bristow	Gennadiy Rozental	"Boost.Test Floating-point comparison diagnostic output does not support radix 10.

This emerged as a problem writing tests for Christopher Kormanyos proposed e_float extended precision float library which uses radix 10.

Tests that fail do not provide sufficient decimal digits to reveal why the test fails.

Numeric_limits is properly specialized for e_float, so max_digits10 is valid (and this is also true for a recent fixed decimal library. 

So I suggest that in test_tools.hpp function set_precision

After dealing with the radix = 2 case,

(and noting that although we would like to rely on max_digits10, older compilers/libraries do not provide it, and the recent MS VC10 wrongly implements float max_digits10 as 8 instead of 9, it is safer to continue to use the original Kahan formula)>

      // Ideally should use max_digits10 if available, and correct! But this always works.
        if( std::numeric_limits<T>::is_specialized && std::numeric_limits<T>::radix 

Add new code to deal with the radix=10 case (but in this case '''we can rely on max_digits10''')

        // If radix = 10, is recent code so assume max_digits10 should be correct.
        // For example, e_float and a fixed decimal package(s) both comply.

        if( std::numeric_limits<T>::is_specialized && std::numeric_limits<T>::radix == 10 )
            ostr.precision( std::numeric_limits<T>::max_digits10 );

(Might also be worth a comment that for other cases, precision will remain at the default value, whatever that is).

This has been tested and works as expected for e_float.


"	Support Requests	closed	Boost 1.51.0	test	Boost Development Trunk	Problem	fixed	floating point radix 10 decimal precision