Add some of `[T]`’s methods to strings and vice versa #1152

P1start · Jun 6, 2015

Add some methods that already exist on slices to strings and vice versa. Specifically, the following methods should be added:

str::chunks
str::windows
str::into_string
String::into_boxed_slice
<[T]>::subslice_offset

Rendered

Kimundi · Jun 6, 2015

Is the reason for adding <[T]>::subslice_offset just symmetry? I'm asking because I'm not sure if that function is actually used by anyone.

P1start · Jun 6, 2015

@Kimundi I’ve wanted to use it in the past, but yeah, it’s mainly just to match the str API. I wouldn’t really care if subslice_offset got removed from str (it’s not very useful), but I’d certainly prefer to either have it for both types or neither, rather than just one.

Gankro · Jun 6, 2015

Is there really a usecase for str::chunks or windows?

gkoz · Jun 6, 2015

Out of curiosity, what is Box<str> for? I haven't encountered any mentions of this type before.

Gankro · Jun 6, 2015

@gkoz In principle it's just a runtime-constructed &'static str (string litteral). one usize thinner than a String, but effectively immutable as a result.

P1start · Jun 6, 2015

@Gankro str::windows could be used to calculate the Sørensen–Dice coefficient of two strings, and str::chunks has been asked for on IRC a few times.

huonw · Jun 6, 2015

Hm, I suspect windows and chunks will encourage bad Unicode practice without a huge amount of benefit other than symmetry. Specifically they will split between combining characters.

SimonSapin · Jun 9, 2015

SimonSapin reviewed Jun 9, 2015

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SimonSapin · Jun 9, 2015

text/0000-slice-string-symmetry.md

+Add the following methods to `str`, presumably as inherent methods:
+
+- `chunks(&self, n: usize) -> Chunks`: Returns an iterator that yields the
+  *characters* (not bytes) of the string in groups of `n` at a time. Iterator


“Character” is kinda ambiguous. (Unicode has four different definitions.) Maybe use chars instead?

krdln · Jun 9, 2015

+1 to functions involving Box<str>. I was surprised they weren't implemented. And it's good to lose those 4/8 bytes sometimes (especially when within an enum).

-1 to windows and chunks. I second @huonw that they encourage bad practices. I think they belong in unicode crate with codepoint_ and grapheme_ variants.

krdln · Jun 10, 2015

I just stumbled upon the lack of str::shift_char() counterpart for a slice. I guess it would also be worth adding.

P1start · Jun 10, 2015

I just stumbled upon the lack of str::shift_char() counterpart for a slice. I guess it would also be worth adding.

@krdln #1058 already adds that, I believe.

comex · Jun 11, 2015

May be out of scope, but I'd like to see some form of find, rfind, replace, and other pattern-based methods added to [T] or Vec<T>. This would be useful, for example, when dealing with a &[u8] which represents a "string" that may not be valid UTF-8 (such as the contents of a Unix OsStr) - or just random binary data, for that matter.

Gankro · Jun 11, 2015

I concur with @huonw on the dubiousness of windows and chunks in the face of combining characters. It's not clear to me how the Sørensen–Dice coefficient is even supposed to interact with utf8 in that regard.

👍 on the Box conversions. Makes sense.

I'm completely indifferent on subslice_offset

alexcrichton · Jun 16, 2015

This RFC is now entering its final comment period.

alexcrichton · Jun 16, 2015

alexcrichton reviewed Jun 16, 2015

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alexcrichton · Jun 16, 2015

text/0000-slice-string-symmetry.md

+
+- `subslice_offset(&self, inner: &[T]) -> usize`: Returns the offset (in
+  elements) of an inner slice relative to an outer slice. Panics of `inner` is
+  not contained within `self`.


I would personally prefer to not add this method to slices just yet, I suspect it won't survive stabilization of strings.

alexcrichton · Jun 16, 2015

alexcrichton reviewed Jun 16, 2015

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alexcrichton · Jun 16, 2015

text/0000-slice-string-symmetry.md

+
+Add the following method to `String` as an inherent method:
+
+- `into_boxed_slice(self) -> Box<str>`: Returns `self` as a `Box<str>`,


Perhaps this could be into_boxed_str? I think we tend to refer to string slices as str instead of slice.

Perhaps this could be an implementation of Into trait? I don’t see this being used enough to warrant a new method. I’d actually argue for deprecation of Vec::into_boxed_slice and implementation of Into trait too.

That's somewhat related to #1153, but relying solely on Into unfortunately isn't without downsides. For example if I have a String and I know that I want to go to a Box<str> using the .into() method would require a type annotation, where a method like this would not. Overall we've been thinking so far that specific conversions (e.g. like this) will have named methods so they can be called ergonomically, but there will also likely be an Into implementation to satisfy generic bounds as well. Now that being said, we haven't yet posted the RFC to clarify these conversion conventions.

alexcrichton · Jun 16, 2015

I also agree with @huonw about being hesitant to add windows/chunks to strings due to unicode fun stuff.

nagisa · Jun 17, 2015

nagisa reviewed Jun 17, 2015

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nagisa · Jun 17, 2015

text/0000-slice-string-symmetry.md

+- `windows(&self, n: usize) -> Windows`: Returns an iterator over all contiguous
+  windows of character length `n`. Iterator element type: `&str`.
+
+- `into_string(self: Box<str>) -> String`: Returns `self` as a `String`. This is


https://github.com/rust-lang/rfcs/pull/1152/files#r32605082 ditto.

sfackler · Jun 21, 2015

The Box<str> methods seem good to me but I share the unicode weirdness concerns above with respect to chunks and windows and am not sold on the utility of subslice_offset.

Gankro · Jun 22, 2015

@P1start the libs team seems pretty unanimous about Box<str> is great, everything else is not. Is this an acceptable result of this RFC, for you?

P1start · Jun 22, 2015

@Gankro Yep, that’s fine by me. I’ll update the RFC soon to include just those methods (and rename into_boxed_slice to into_boxed_str unless anyone has any objections).

P1start · Jun 27, 2015

RFC updated, removing str::windows, str::chunks, and <[T]>::subslice_offset.

alexcrichton · Jul 1, 2015

The consensus of the libs team is to merge this RFC, so I will do so. Thanks again @P1start!

aturon · Jul 1, 2015

Tracking issue.

Add some of `[T]`’s methods to `str` and vice versa

e4372c4

alexcrichton added the T-libs label Jun 6, 2015

Gankro self-assigned this Jun 11, 2015

alexcrichton added the final-comment-period label Jun 16, 2015

Remove `str::{windows,chunks}` and `<[T]>::subslice_offset`

566bb70

alexcrichton referenced this pull request Jul 1, 2015
Closed
Add conversions from Box<str> and String #26697

alexcrichton merged commit 566bb70 into rust-lang:master Jul 1, 2015

aturon referenced this pull request Jul 1, 2015
Closed
Tracking issue for Add some of `[T]`’s methods to strings and vice versa (RFC 1152) #26729

bluss added a commit to bluss/rust that referenced this pull request Aug 12, 2015

Rename String::into_boxed_slice -> into_boxed_str
This is the name that was decided in rust-lang/rfcs#1152, and it's better if we say “boxed str” for `Box<str>`.

22dbf84

bluss referenced this pull request Aug 12, 2015
Merged
Rename String::into_boxed_slice -> into_boxed_str #27696

bluss added a commit to bluss/rust that referenced this pull request Aug 13, 2015

Rename String::into_boxed_slice -> into_boxed_str
This is the name that was decided in rust-lang/rfcs#1152, and it's better if we say “boxed str” for `Box<str>`.

80456ac

Centril unassigned Gankro Nov 23, 2018

Centril added the A-slice label Nov 23, 2018

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Add some of `[T]`’s methods to strings and vice versa #1152

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alexcrichton merged commit `566bb70` into rust-lang:master Jul 1, 2015