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.

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NetMageSCW a day ago | parent | next [-]

Maybe you should correct the errors in your post before worrying about the code.

	▲	dimview a day ago \| parent [-]
		Corrected the dates, thank you! What are the other errors?

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nomel a day ago | parent | prev [-]

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!

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dimview a day ago | parent [-]

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.

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nomel 20 hours ago | parent [-]

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

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