> However, you don’t need code point indexing here, byte indexing works fine! UTF8 is designed so that you can check if you’re on a code point boundary even if you just byte-index directly.

Yes, UTF-8 is self-resynchronizing in either direction. I.e., if you pick a random byte index into a UTF-8 string, you can check if that byte's value is the start of a codepoint, and if not then you can scan backwards (or forward) to find the start of the current (or next) codepoint. Do be careful not to overrun the bounds of the string, if you're writing C code anyways.

Do note that start-of-codepoint is not the same thing as start-of-grapheme-cluster or start-of-character.

Also, TFA doesn't touch at all on forms and normalization. And I think TFA is confused about "meaning". Unicode codepoints very much have meaning, and that had better not change. TFA seems to be mostly about indexing into strings, and that content is fine.

> One very common misconception I’ve seen is that code points have cross-language intrinsic meaning.

Well, maybe that depends on what the meaning of "meaning" is.

Unicode codepoints have normative meanings -- that is, meanings assigned by the Unicode Consortium. Those "meanings" are embodied in a) their names and descriptions, b) their normative glyphs. Some codepoints are combining codepoints, and their meaning lies in the changes to the base codepoint's glyph when applied -- this is certainly a kind of "meaning".

But of course people can use codepoints (really, characters) in ways which do not comport to the meanings assigned by the UC. That's fine, of course. The real meanings of the words we write and how we use them, and the glyphs they are composed of, vary over time because human language evolves.

But TFA writes "cross-language intrinsic meaning". That's a more specific claim that is more likely to be true.

It's certainly true that Indic language glyphs have no meaning to me when mixed with Latin scripts, since I know nothing about them, though I can look up their meaning, and I can learn about them. And it's also true that confusable codepoint assignments (e.g., some Greek charaters look just like Latin characters, and vice-versa) may not, for the reader, have the UC's intended meaning, since to the reader the only meaning will only be the rendered glyph's rather than the codepoint's! After all, being confusable, the reader isn't likely to notice that some glyph is not Latin but Greek (or whatever).

But if some text does not mix confusable scripts with the intent of creating confusion, and if it is clear to the reader what is intended, then a reader familiar with the scripts (and languages) being used in the text will be able to discern intended meaning, and the UC-assigned meanings of the codepoints used will be... meaningful even though the text is mixed-script text.

So, yes, with caveats, Unicode codepoints do have "cross-language intrinsic meaning".

IMO, it would have been better for TFA not to mix the two things, codepoint meaning and string indexing issues.

Also, string indexing is just not needed. In general you have to parse text from first code unit to last. You might tokenize text, and then indexing into a sequence of tokens might have meaning / be useful, but indexing into UTF-8/16/32 by code unit is not really useful.