Re: [boost] Decimal floating point library

From: Stefan Slapeta (stefan_at_[hidden])
Date: 2006-03-03 05:10:02

Beman Dawes wrote:

[...]
> 
> I assume you meant "the story *isn't* over here":-)
> 

Anyway ... :-)

> It has been quite a while, but IIRC the three proposed types are also 
> supposed to be useful for decimal integers. To emphasize that, 
> "floating-point" was removed from the name of the proposal.
> 
> Perhaps Robert can clarify.
> 

They are for sure. A decimal with a zero scale is an integer.

>>
>>(1) an arbitrary length integer type
>>(2) an arbitrary length decimal floating point type, which is a
>>    combination of (1) with an integer-like scale so that
>>    decimal_value = large_integer_value / 10 ^ scale
>>(3) three specializations of (2) to provide the IEEE and TR2
>>    conforming interface (32, 64, 128 digits)
> 
> 
> "The best is the enemy of the good," as Voltaire said.
> 

yes, and "multa petentibus multa desunt" ;-)

> We don't have (1) or (2) for binary arithmetic yet. How is decimal special 
> in that regard?
> 

Why would we need that for binary arithmetic?

> 
> It might be possible to break the job down into:
> 
> (A) A core decimal arithmetic engine (presumably tailorable to different 
> lengths, and replicable by hardware if chip companies do start providing 
> hardware engines.)
> (B) Public interfaces to the core engine.
> (C) A test suite for the core engine, concentrating on arithmetic 
> correctness.
> (D) A test suite for the public interfaces, concentrating on interface 
> correctness.
> 
> If you make some progress on (A), perhaps others might volunteer to tackle 
> the other parts.
> 

I'll see what I can do, but it's a large job. I'm off now for 4 weeks 
and I'll create something to start with afterwards. And we should also 
take the discussions during the boost decimal review into account.

Stefan