Re: [boost] New numeric data type proposal

Subject: Re: [boost] New numeric data type proposal
From: John Maddock (boost.regex_at_[hidden])
Date: 2014-03-25 14:45:24

> Do you have a place I can read about how the implementation of that one was intended?

No sorry, it was discussed/requested when the library was reviewed 
that's all.  There are some alternative implementations on the net, but 
I can't find them right now :-(

John.

> I think the differences between the 2 should be in the implementation details and not in the interfaces.
>
> The idea behind keeping the Qnum was to maximise the usable numbers in the mantissa.
> In an scenario where the Q (num and denim) stabilises, the useful representable values of the mantissa is as large as possible.
> While in the other approach, suppose that the Q should stabilise at 1500/1501 then, Qdenom is 1501, but 1500 is present multiplier of every mantissa.
> This way you waste 1499 every 1500 numbers in the mantissa representation and probably need to increase the size of the mantissa (or not, depends on the use case).
> In the other side, finding Qnum is not necessarily easy, it increases the quantity of computation needed to find the common factor between 2 operands and may increase the quantity of disagreements (1/3 and 2/3 are now not in agreement).
>
> Regards, Damian
>
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