— Turing complete with a stack of 0xdeadbeef



Ending the Swift Weekly Brief

Taking an indefinite hiatus from writing the newsletter, and looking for a new owner

Next week’s issue of Swift Weekly Brief will be its 100th and final issue. I started this newsletter a little over two years ago, covering the initial open sourcing of Swift, the 3.0 release, the 4.0 release, and many significant milestones in-between for the language and the community. With few exceptions, there was a new issue every week thanks to the other amazing writers and contributors. The newsletter quickly became an important resource for the Swift community. Because of this, I’m sure many of you will be saddened to hear that the 100th issue will be the last. At least, Issue #100 will be the last issue for me, for now — but if someone from the community is willing to take over this project, it can continue.

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Floating-point Swift, ulp, and epsilon

Exploring floating-point precision

Epsilon. ε. The fifth letter of the Greek alphabet. In calculus, an arbitrarily small positive quantity. In formal language theory, the empty string. In the theory of computation, the empty transition of an automaton. In the ISO C Standard, 1.19e-07 for single precision and 2.22e-16 for double precision.

The other day I was attempting to use FLT_EPSILON (which I later learned was laughably incorrect) when the Swift 4 compiler emitted a warning saying that FLT_EPSILON is deprecated and to use .ulpOfOne instead. What the hell is ulpOfOne? I read the documentation and then everything made sense — ha, just kidding. The FloatingPoint.ulpOfOne docs generously describe the static variable as the unit in the last place of 1.0 — whatever that means. Let’s find out.

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When your app is used in unexpected ways

PlanGrid as a digital archaeological tool

PlanGrid is a productivity app for construction fieldworkers. The easiest way to explain it to software developers is that it’s like an IDE, Git, and GitHub or JIRA — but for construction. Think of all the amazing software tools we have to do our jobs as programmers. The equivalent tools for construction simply did not exist before PlanGrid, and they still have a lot of room to grow.

As software developers, we build software for specific purposes. We anticipate that people will use an app in certain ways. Yet, we often discover that users are behaving differently than we expected. They hack a custom, “unsupported” workflow to workaround an app’s unintended limitations. Once we realize this, we have the power to turn these user workarounds into first-class features. However, sometimes we find that our apps are being used in totally different, unimaginable ways.

At PlanGrid, we recently discovered that the app was being used as a digital archaeological tool.

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