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#java#boehm#library#port#hans#https#add#cas#exp#dates

Discussion (24 Comments)Read Original on HackerNews

__alexs•about 20 hours ago
> Hans Boehm built a Java library for this in the 1980s and 90s

Hans is such a prolific programmer that he wrote a Java library before Java was even invented?

tomjakubowski•about 19 hours ago
The article has so many of the hallmarks of LLM writing, naturally it will have some hallucinated factoids too. "What that gives you: [bullet list]", "What got ported: [bullet list]", "foo: x, y, just z"

Boehm's Java library has copyright dates of 1999 and 2001-2004. https://www.hboehm.info/new_crcalc/CR.java

The whitepaper was only published in 2005: https://www.sciencedirect.com/science/article/pii/S156783260...

I have a dimview now of the blog, and of this Swift port of the library, indeed.

dimview•about 16 hours ago
Thank you. Of course the dates were out of order. The Java library (com.hp.creals) is 1999-2004, paper is from 2005. Unfortunate price of LLM-assisted development. Corrected.
nxobject•about 19 hours ago
Well, you know, you go into your Smalltalk-80 workstation for a hack sesh, and an all-nighter later you end up with an implementatkon of Swing...
bla3•about 19 hours ago
> I built one, by porting Boehm’s engine. > It’s 2026, so I didn’t hand-write the port. I directed Opus 4.8 to translate the source line by line into Swift

I wish I could filter out stuff like this. Cool work by Hans Boehm, but what's the value add in this blog post.

B1FF_PSUVM•about 18 hours ago
Read. Guy knows what he's doing.
IAmBroom•about 4 hours ago
You mean his AI wrote something you like... which is factually incorrect, so it's basically fanfic.
dimview•4 days ago
Author here. I could not find a constructive‑reals calculator on iPhone, so I ported the engine Android uses: Hans Boehm's com.hp.creals plus AOSP's UnifiedReal/BoundedRational. Used Opus 4.8 to do the port and Fable 5 for the review.

Fable 5 caught a couple of real concurrency bugs the port introduced while adapting Java's synchronized/AsyncTask to Swift concurrency, including one that was a memory‑safety bug on shared singletons like π, not just a wrong digit. None would have shown up in the unit tests. Writeup has the details.

It's an early iPhone TestFlight beta (link in the post); happy to go deep on either the constructive‑reals side or the AI‑assisted‑dev side.

NetMageSCW•about 19 hours ago
Maybe you should correct the errors in your post before worrying about the code.
dimview•about 16 hours ago
Corrected the dates, thank you! What are the other errors?
nomel•about 19 hours ago
The old HP calculators, and their emulators, have a computer algebra system, for symbolic maths, that supported this. The user interfaces leave much to be desired, but some also have reverse Polish notation!
dimview•about 17 hours ago
This is different from a CAS. For example, if you ask it to do exp(100)+1-exp(100), it does not rearrange and cancel out the two exp(100)s. Instead, it does exp, addition, and subtraction, all with as many digits as you ask for.
nomel•about 13 hours ago
Sure. I was speaking to the what, not how.

> that doesn’t round at all. It computes with constructive real numbers: every result is exact, and you can scroll any answer for as many correct digits as you want.

A CAS is a practical way to achieve this, where everything is stored symbolically, with no rounding, until final calculation. Unlimited precision was through Erable [1]. This was included with/as HP49 CAS, but was an add-on with HP48. Many HP48 are on the iOS app store. The one I tried about a decade ago had the add-on, and I see many still there (but not sure if they have the add-on).

The "S" in CAS is "system", so it's a bit open.

[1] https://en.wikipedia.org/wiki/Erable

quixoticelixer-•about 19 hours ago
I don't get why this is a big deal. All the calculators I've used have been rectangle.
jagraff•about 20 hours ago
Very interesting, thank you for posting! I'm curious - roughly how many tokens do you think you used during the initial port and subsequent bug hunting and fixes?
dimview•about 16 hours ago
For Opus 4.8, 142.3k input, 2.0m output for the entire project. No longer have access to Fable 5 to check.
piinbinary•about 20 hours ago
It would also be fun to have a full computer algebra system (like maxima) on a phone
xigoi•about 7 hours ago
https://webdev4.gitlab.io/fdroid-website/en/packages/jp.yhon...
dimview•about 17 hours ago
That should be doable, too. Maybe as a next project.
htx80nerd•about 20 hours ago
btw if you turn the iphone calc into landscape mode and switch you scientific calc it does Ramanujan's constant without rounding, but stops after the twelve 9s.
dimview•about 17 hours ago
Correct, but if you don't know the next digit is 2, you can think it's all 9s, another representation of an integer number.
Jblx2•about 20 hours ago
Edit: Whoops. My bad. This must have been a HN "second chance" winner.
badc0ffee•about 19 hours ago
That looks like a link right back to this thread?
ColinWright•about 19 hours ago
Er, that's this submission.