Skip to content

reword faq to remove reference to indexing strings #19345

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 1 commit into from
Closed

reword faq to remove reference to indexing strings #19345

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion src/doc/complement-lang-faq.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -108,7 +108,7 @@ The `str` type is UTF-8 because we observe more text in the wild in this encodin

This does mean that indexed access to a Unicode codepoint inside a `str` value is an O(n) operation. On the one hand, this is clearly undesirable; on the other hand, this problem is full of trade-offs and we'd like to point a few important qualifications:

* Scanning a `str` for ASCII-range codepoints can still be done safely octet-at-a-time, with each indexing operation pulling out a `u8` costing only O(1) and producing a value that can be cast and compared to an ASCII-range `char`. So if you're (say) line-breaking on `'\n'`, octet-based treatment still works. UTF8 was well-designed this way.
* Scanning a `str` for ASCII-range codepoints can still be done safely octet-at-a-time. If you use `.as_bytes()`, pulling out a `u8` costs only O(1) and produces a value that can be cast and compared to an ASCII-range `char`. So if you're (say) line-breaking on `'\n'`, octet-based treatment still works. UTF8 was well-designed this way.
* Most "character oriented" operations on text only work under very restricted language assumptions sets such as "ASCII-range codepoints only". Outside ASCII-range, you tend to have to use a complex (non-constant-time) algorithm for determining linguistic-unit (glyph, word, paragraph) boundaries anyways. We recommend using an "honest" linguistically-aware, Unicode-approved algorithm.
* The `char` type is UCS4. If you honestly need to do a codepoint-at-a-time algorithm, it's trivial to write a `type wstr = [char]`, and unpack a `str` into it in a single pass, then work with the `wstr`. In other words: the fact that the language is not "decoding to UCS4 by default" shouldn't stop you from decoding (or re-encoding any other way) if you need to work with that encoding.

Expand Down