A calculator that doesn't round

3 days ago

Constructive Calculator is an iPhone app that uses constructive real arithmetic, allowing exact results without rounding, and enabling scrolling for as many digits as needed.
It can compute expressions like Ramanujan's constant (exp(π√163)), which appears as an integer but reveals differences upon scrolling, and exp(100) + 42 − exp(100) returns exactly 42 by evaluating to necessary precision.
The app is built by porting Hans Boehm's Java library for constructive reals to Swift, with AI assistance from Opus 4.8 for translation, and includes layers for symbolic exactness and a SwiftUI front end.
Porting challenges included adapting Java concurrency features to Swift, leading to bugs like incorrect actor isolation and cache races, which were caught by a separate AI model review.
Limitations include undecidability of equality in constructive real arithmetic, so some results display as approximations even when exact, similar to Android's calculator.
The app is available as an early TestFlight beta for iPhone, with recent additions like standard normal CDF and inverse functions implemented via new constructive series.

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