On Oct 3, 2011, at 7:46 AM, erik quanstrom <quans...@quanstro.net> wrote:
>> On Oct 3, 2011, at 4:41 AM, tlaro...@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. >>> >> Integer & rational arithmetic is guaranteed in Scheme and some other >> languages. In an R5RS compliant Scheme implementation you have for >> example (/ 5 7) => 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! > > i think you've got it there. how do i stuff 5/7 in a 32-bit ethernet > register? > 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 fight. Scheme has conversion functions + macros to do what you want. Also note that 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 well as for generating code for a custom network processor. This NP had a 512 bit 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 (+ (quotient 512-bit-reg 2^32) new-32-bit-value)). Could've done in C but this was more fun and far fewer lines of code and far quicker to develop! I could represent 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!
