Formatting floating point numbers

Re:Formatting floating point numbers by tomxor on Friday June 14, 2019 @09:22AM (#20182718)

haha, yes it's a terrible name, such arrogance to suggest fitting infinite things into a very finite thing. In fact they couldn't even call it rational, because even after the precision limitation it's a subset of rationals (where representation error comes from due to base)... Inigo Quilez cam up with a really interesting way around this limitation where numbers are encoded with a numerator and denominator, he called "floating bar", this essentially does not have representation error, but it will likely hit precision errors sooner or at least in a different way (it's kinda difficult to compare directly).

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Re:Formatting floating point numbers by bunderbunder on Friday June 14, 2019 @10:13AM (#20183161)

Yeah, that is more what I'm on about. I can accept that a computer's `int` type is not an infinite set, even if it does cause problems at the boundaries. It feels like more of a little white lie to me.

Whereas, even between their minimum and maximum values, and even subject to their numeric precision, there are still so many rational numbers that an IEEE float can't represent. So it's not even a rational. Nor can it represent a single irrational number, thereby failing to capture one iota of what qualitatively distinguishes the real numbers. . . if Hacker News supported gifs, I'd be inserting one that features Mandy Patinkin right here.

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Re:Formatting floating point numbers by tomxor on Friday June 14, 2019 @10:39AM (#20183364)

Yeah, I think this is the single aspect that everyone finds unintuitive, everyone can understand it not having infinite precision or magnitude. It's probably a very reasonable design choice if we could just know the reasoning behind it, I assume it will be mostly about practicality of performance and implementing the operators that have to work with the encoding.

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Re:Formatting floating point numbers by romwell on Friday June 14, 2019 @09:31PM (#20187923)

>Inigo Quilez cam up with a really interesting way around this limitation where numbers are encoded with a numerator and denominator, he called floating bar

Thanks for the read! More fun than the original article to my taste :)

Here's the link, since Googling "floating bar" nets you very different results:

http://www.iquilezles.org/www/articles/floatingbar/floatingb...

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Re:Formatting floating point numbers by tomxor on Saturday June 15, 2019 @04:26AM (#20188944)

I just remember his name, writes lots of interesting stuff :)

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Re:Formatting floating point numbers by romwell on Monday June 17, 2019 @07:27PM (#20208310)

I always wonder if he ever says "My name is Inigo Quilez. Prepare to learn!".

My favorite post by him is where he explains that you never need to have trigonometry calls in your 3D engine. Because everyone now and then you still see "educational" article in the spirit of "learn trig to spin a cube in 3D!" :/

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Re:Formatting floating point numbers by tomxor on Tuesday June 18, 2019 @01:05PM (#20215357)

Yeah, I've noticed in physics programming in other peoples code you can often come across the non-trig ways of doing things that avoid unit vectors and rooting etc (which are both elegant and efficient)... However i've never personally come across an explicit explanation or "tutorials" of these targeted at any level of programmer's vector proficiency. Instead i've always discovered them in code, and had to figure out how they work.

I guess the smart people writing a lot of this stuff just assume everyone will derive them as they go. That's why we need more Inigo Quilez's :D to lay it out for us mere mortals and encourage it's use more widely.

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Re:Formatting floating point numbers by gumby on Friday June 14, 2019 @10:14AM (#20183169)

Common Lisp has had a rational number Type since the 1980s at least, presumably inherited from MACSYMA

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