turing complete with a stack of 0xdeadbeef

Writing by tag

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.

Continue…