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From: Bakul Shah <bakul@bitblocks.com>
Date: Mon,  3 Oct 2011 08:29:40 -0700
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] circular fonctions: precision?
Topicbox-Message-UUID: 302a0f16-ead7-11e9-9d60-3106f5b1d025

On Oct 3, 2011, at 7:46 AM, erik quanstrom <quanstro@quanstro.net> wrote:

>> On Oct 3, 2011, at 4:41 AM, tlaronde@polynum.com wrote: >>
>>> But to come back to programming, when calculus is the crux, the more
>>> common/known even new!  programming languages are not great tools,
>>> and "portability" i.e.  proved accuracy of the implementation for a
>>> wide range of hardware/software is fuzzy.  And it's amazing to see
>>> how one can rapidly face errors even with very basic computations.
>>> And even with integer arithmetic, not much help is guaranteed by
>>> languages.
>>>=20
>> Integer & rational arithmetic is guaranteed in Scheme and some other
>> languages.  In an R5RS compliant Scheme implementation you have for
>> example (/ 5 7) =3D> 5/7.  (If only people get over their irrational
>> fear of prefix syntax they would discover a great little language in
>> Scheme.) But most prog.  languages do not specify minimal required
>> accuracy on standard floating pt.  functions.  May be because most
>> language hackers are not numerical analysts!
>=20
> i think you've got it there.  how do i stuff 5/7 in a 32-bit ethernet regi=
ster?
> if you're close to the h/w, it's probablly just confusing to fight it.

Ethernet ctlrs have FP registers these days? Wow! It is just a different fig=
ht. Scheme has conversion functions + macros to do what you want. Also note t=
hat most people do not work as closely to h/w as perhaps you or I do. And of=
 course, you don't have to use just one language.

Funny you mention h/w. I have used scheme in the past for h/w testing as wel=
l as for generating code for a custom network processor. This NP had a 512 b=
it barrel shifter (could hold an entire 64 byte pkt and we could poke at any=
 bitfield upto 32 bits in length). In my test library a 'shift' was (+ (quot=
ient 512-bit-reg 2^32) new-32-bit-value)). Could've done in C but this was m=
ore fun and far fewer lines of code and far quicker to develop! I could repr=
esent an entire test pkt as a single number and shift into the barrelshifter=
 etc. No need to worry about grotty indexing or off by 1 errors!=20