Truths programmers should know about case (2018)

In this post I’m primarily using “uppercase” and “lowercase”, because the Unicode Standard uses those terms when talking about case. But applying case mapping to uppercase doesn’t change it, and applying case mapping to lowercase doesn’t change it, so by definition (3) of case, this character answers “yes” to both “are you uppercase?” This may seem like it would introduce needless confusion, but it means definition (3) works on any sequence of Unicode characters, and allows case mapping algorithms to be simpler (characters that aren’t cased just map to themselves).

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