Jesse Squires

— Turing complete with a stack of 0xdeadbeef


How to run sysdiagnose on iOS

And on all the Apple things

Updated: 09 Feb 2018

When you file a radar for a bug on one of Apple’s platforms, you should (usually) always attach a sysdiagnose. A sysdiagnose provides a lot of helpful information for the person who is trying to understand how the bug happened. Amongst other things, it contains logs from various parts of the OS, and all recent crash logs. Without it, the person on the other end of your report inside Apple may not be of much help. On macOS running sysdiagnose is somewhat common, but what about iOS?

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Ending the Swift Weekly Brief

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

Updated: 08 Feb 2018

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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