4 ms·

> strings aren’t actually simple arrays of characters in Rust Are you talking about them being a container with a pointer to the actual array, and also a size

> strings aren’t actually simple arrays of characters in Rust Are you talking about them being a container with a pointer to the actual array, and also a size and etc?

Skunkleton 6y ago
char is usually some single byte of data. Characters can be multiple bytes. Slicing a string on character boundaries is more coarse grained than slicing on byte boundaries.
- estebank 6y ago
  char in Rust is 32bits, so it has a 1:1 mapping to Unicode glyphs. You might also want to care about grapheme clusters, but those are not part of the stdlib.
  - toast0 6y ago
    Unicode codepoints; glyphs may take multiple codepoints.
    - estebank 6y ago
      You are, of course, correct.
nicklecompte 6y ago
Right - the point is that &str isn't syntactic sugar / alias / etc for &[u8] and it would be confusing to have a notation that suggested otherwise.
seoaeu 6y ago
In C, strings can hold invalid unicode. However, in Rust a str is guaranteed to be valid utf-8. For added confusion, Rust has a `char` type which is actually 32-bits. You can create arrays of them, but the resulting string would be in utf-32 and thus incompatible with the normal `str` type.
- Animats 6y ago
  let s = "hello world".to_string(); for ch in s.chars() { print!({},ch); } will iterate through a string character by character. That's the most common use of the "char" type - one at a a time, not arrays of them. Although the proper grapheme form is: use unicode_segmentation::UnicodeSegmentation; // 1.7.1 let s = "hello world".to_string(); for gr in UnicodeSegmentation::graphemes(s.as_str(), true) { print!("{}", gr) } This will handle accented characters and emoji modifiers. A line break in the middle of a grapheme will mess up output. By the way, open season for proposing new emoji starts tomorrow.[1] [1] http://blog.unicode.org/2020/09/emoji-150-submissions-re-open-april-2.html http://blog.unicode.org/2020/09/emoji-150-submissions-re-ope...
  - TheGrassyKnoll 6y ago
    Thanks for the code snippet, however (kind of a Rust newbie here) $ cargo install unicode_segmentation (chokes) $ cargo install unicode-segmentation (seems to work) and in Cargo.toml [dependencies] unicode-segmentation = "1.7.1" (seems to work) yet in the code, its: use unicode_segmentation::UnicodeSegmentation; Why couldn't they be consistent using a dash vs. an underscore ?
    - steveklabnik 6y ago
      You don’t cargo install libraries; the cargo.toml line is the right thing. You can’t use -s in Rust identifiers, so they need to be normalized to _ to be referred to in code.
    - estebank 6y ago
      Identifiers in Rust can't have dashes (rustc will never rely on whitespace for proper tokenization). It is arguable that because of that crates should not have dashes in their name. cargo was changed to automatically convert dashes to underscores for convenience because some dislike underscores in names. I personally think this is an unnecessary source of confusion and now I would make all tools (mainly cargo) treat them interchangeably.

> strings aren’t actually simple arrays of characters in Rust Are you talking about them being a container with a pointer to the actual array, and also a size and etc?

Skunkleton 6y ago

char is usually some single byte of data. Characters can be multiple bytes. Slicing a string on character boundaries is more coarse grained than slicing on byte boundaries.

estebank 6y ago
char in Rust is 32bits, so it has a 1:1 mapping to Unicode glyphs. You might also want to care about grapheme clusters, but those are not part of the stdlib.
- toast0 6y ago
  Unicode codepoints; glyphs may take multiple codepoints.
  - estebank 6y ago
    You are, of course, correct.

nicklecompte 6y ago

Right - the point is that &str isn't syntactic sugar / alias / etc for &[u8] and it would be confusing to have a notation that suggested otherwise.

seoaeu 6y ago

In C, strings can hold invalid unicode. However, in Rust a str is guaranteed to be valid utf-8. For added confusion, Rust has a `char` type which is actually 32-bits. You can create arrays of them, but the resulting string would be in utf-32 and thus incompatible with the normal `str` type.

Animats 6y ago
let s = "hello world".to_string(); for ch in s.chars() { print!({},ch); } will iterate through a string character by character. That's the most common use of the "char" type - one at a a time, not arrays of them. Although the proper grapheme form is: use unicode_segmentation::UnicodeSegmentation; // 1.7.1 let s = "hello world".to_string(); for gr in UnicodeSegmentation::graphemes(s.as_str(), true) { print!("{}", gr) } This will handle accented characters and emoji modifiers. A line break in the middle of a grapheme will mess up output. By the way, open season for proposing new emoji starts tomorrow.[1] [1] http://blog.unicode.org/2020/09/emoji-150-submissions-re-open-april-2.html http://blog.unicode.org/2020/09/emoji-150-submissions-re-ope...
- TheGrassyKnoll 6y ago
  Thanks for the code snippet, however (kind of a Rust newbie here) $ cargo install unicode_segmentation (chokes) $ cargo install unicode-segmentation (seems to work) and in Cargo.toml [dependencies] unicode-segmentation = "1.7.1" (seems to work) yet in the code, its: use unicode_segmentation::UnicodeSegmentation; Why couldn't they be consistent using a dash vs. an underscore ?
  - steveklabnik 6y ago
    You don’t cargo install libraries; the cargo.toml line is the right thing. You can’t use -s in Rust identifiers, so they need to be normalized to _ to be referred to in code.
  - estebank 6y ago
    Identifiers in Rust can't have dashes (rustc will never rely on whitespace for proper tokenization). It is arguable that because of that crates should not have dashes in their name. cargo was changed to automatically convert dashes to underscores for convenience because some dislike underscores in names. I personally think this is an unnecessary source of confusion and now I would make all tools (mainly cargo) treat them interchangeably.