Boost logo

Boost :

Subject: Re: [boost] [Boost.FixedPoint] Choose notation
From: Dmitriy Gorbel (dmitriycpp_at_[hidden])
Date: 2013-04-29 11:51:04

 Michael Marcin-3 wrote
> I dislike the names. I don't really understand what the first 2 types
> have to do with fixed-point math, other than maybe as an implementation
> detail or degenerate fixed-point type (0 fractional bits).

I add cardinal and integral types to the proposal because
this types required by C++1y proposal. I agree, this types
quite illogical. Maybe, this types proposed for supporting big integers,
but I think for big integers better use Boost.Multiprecision library.

It's easy to implement integral types based on fractional,
using template aliases, for example:
template<size_t Range> using cardinal = nonnegative<Range, 0>;
template<size_t Range> using integral = negatable<Range, 0>;

What community think about this?
Should library support integral fixed point types?

Neal Becker wrote
> Thank you. The last time we discussed this topic, the issue was not one
> of
> notation, but of different semantics that were desired by different end
> users of
> a fixedpoint type.
> I think there were several areas of disagreement - but perhaps primary was
> whether arithmetic operations would produce different types or the same
> types,
> and how to handle arithmetic between mixed types. For example, does
> multiplication of 2 8-bit quantities promote to 16 bits or not.
> My preference is/was that no implicit conversion was ever performed and
> that it
> always had to be explicit. This is partly because the primary consumer
> for this
> technology (I think) is those working on FPGA or ASIC hardware - and they
> should
> always be aware of any such conversions.

Best way - conversion policy,
when user can choose between implicitly/explicitly conversion.
I will try to implement both variants.


View this message in context:
Sent from the Boost - Dev mailing list archive at

Boost list run by bdawes at, gregod at, cpdaniel at, john at