October 2025
Intermediate to advanced
100 pages
2h 27m
English
Content preview from Kotlin Brain TeasersBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Discussion
One of the basic laws of equality is that a value is always equal to itself. Given two copies of the same input, the equals operator (==) should always return true. But the special value NaN, short for Not a Number, doesn’t follow that rule. Or does it?
Treat NaN as a Double and it follows the letter of the IEEE 754 specification for floating-point numbers, which stipulates that NaN is never equal to itself. But label the same NaN value with a less specific type, such as Any, and it goes back to behaving like an ordinary Kotlin object.
The result is a self-contradicting comparison that can return two different results for the same pair of inputs, depending on the types you give to those inputs.
Undefined Value
To make all your hardware ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.