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Subject: Re: [boost] floating point FUD
From: Thomas Klimpel (Thomas.Klimpel_at_[hidden])
Date: 2010-01-24 13:05:56

Phil Endecott wrote:
> Is it time to raise the idea of a Boost fixed-point library again?

A long time ago, I read
The developed methods were also analyzed in a fixed-point context. But trying to think about fixed-point numbers, I soon realized that I don't even understand the basics, like negative numbers or multiplication. I think I did a web search at that time, but wasn't able to find much introductory material.

However, I just did a web search again, and there was an extensive Wikipedia article on the subject, with many interesting references. I found the following in the first reference:

> While there is nothing particularly difficult about this subject,
> I found little documentation either in hardcopy or on the
> web. What documentation I did find was disjointed, never
> putting together all of the aspects of fixed-point arithmetic
> that I think are important. I therefore decided to develop
> this material and to place it on the web not only for my own
> reference but for the benefit of others who, like myself,
> find themselves needing a complete understanding of the issues
> in implementing fixed-point algorithms on platforms utilizing integer arithmetic.

So perhaps it was really difficult to find introductory material on the web a long time ago, but the situation seems to have changed in the meantime. (Perhaps I will read some of the introductory material when I find time.) I also read the following on Wikipedia:

> ISO/IEC TR 18037[5] specifies fixed-point data types
> for the C programming language; vendors are expected
> to implement the language extensions for fixed point arithmetic
> in coming years. Fixed-point support is implemented in GCC.[6][7]

This looks like fixed-point support will really become "mainstream" soon. How is this related to C++ and the idea of a Boost fixed-point library?


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