# ANN: StringUnits.jl

**URL:** <https://discourse.julialang.org/t/ann-stringunits-jl/112202>\
**Category:** Package Announcements\
**Tags:** question, announcement, strings, indexing, units\
**Created:** [March 27, 2024, 10:09pm UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202 "2024-03-27T22:09:52Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![mnemnion](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mnemnion/32/206596_2.png) [@mnemnion](https://discourse.julialang.org/u/mnemnion)\
**Post date:** [March 27, 2024, 10:09pm UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202/1 "2024-03-27T22:09:52Z")

</div>

Inspired by this [lengthy thread](https://discourse.julialang.org/t/stringindex-idea-julia-2-0/107185), which I jumped into [somewhat later](https://discourse.julialang.org/t/stringindex-idea-julia-2-0/107185/68), I’ve implemented the idea as [StringUnits.jl](https://github.com/mnemnion/StringUnits.jl).

Pretty straightforward:

```julia
julia> "aβc∅👨🏻‍🌾efg"[2ch:4ch]
"βc∅"

julia> "aβc∅👨🏻‍🌾efg"[5gr]
"👨🏻‍🌾"

julia> "aβc∅👨🏻‍🌾efg"[3gr:6gr]
"c∅👨🏻‍🌾e"

```

Units can be mixed:

```julia
julia> "aβc∅👨🏻‍🌾efg"[2ch+1gr:3ch+2gr]
"c∅👨🏻‍🌾e"

```

Currently, negative indices of any sort are not supported, although I’d like to add that, time permitting.

Oh, and you can use normal byte-based indices as well:

```julia
julia> "aβc∅👨🏻‍🌾efg"[5:5+3gr]
"∅👨🏻‍🌾ef"

```

More details may be found in the [documentation](https://mnemnion.github.io/StringUnits.jl/).

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**Author:** ![rafael.guerra](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rafael.guerra/32/216610_2.png) [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)\
**Post date:** [March 27, 2024, 11:12pm UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202/2 "2024-03-27T23:12:01Z")

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FWIW, have you considered other names?

- StringIndexingUnits
- StringIndexers

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<div class="post-metadata">

**Author:** ![mnemnion](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mnemnion/32/206596_2.png) [@mnemnion](https://discourse.julialang.org/u/mnemnion)\
**Post date:** [March 27, 2024, 11:52pm UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202/3 "2024-03-27T23:52:25Z")

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The discussion thread I linked to had several names, including, of course, `StringIndex`.

I went with `StringUnits` because they’re units. Saying “five graphemes” is much like saying “five meters”, so `StringUnits` spells that `5gr`, just like Unitful.jl spells the latter `5m`.

`StringIndex` was/is a proposal to change how Julia itself does indexing, and differs in certain particulars from the approach taken in this package, although various contributors to that thread fleshed out basically all of the ideas which went into the implementation, at one point or another in it.

`StringIndexingUnits` seems redundant, and no, I never considered that, or `StringIndexers`.

I did consider naming the package `StringIndices`, but I took a look at how `Unitful` does units and decided on the name I ultimately chose. We have a string index, the code-unit. This adds additional units.

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**Author:** ![\_bernhard](https://avatars.discourse-cdn.com/v4/letter/_/bc79bd/32.png) [@\_bernhard](https://discourse.julialang.org/u/_bernhard)\
**Post date:** [March 28, 2024, 10:07am UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202/4 "2024-03-28T10:07:27Z")

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Nice package!  
Regarding the name - while I see your point on the similarity to regular units, I think where the comparison to meters fails is that there is no fixed conversion factor between chars, graphemes, codepoints.

just my 2c worth of bike shedding

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**Author:** ![goerz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/goerz/32/3269_2.png) [@goerz](https://discourse.julialang.org/u/goerz)\
**Post date:** [March 28, 2024, 10:42am UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202/5 "2024-03-28T10:42:41Z")

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The package went through the standard 3-day registration process, which would have been the time to comment on package naming. At this point, while it may not be the perfect or most inspired name, it’s what we have. I’d recommend following the `#new-packages-feed` on Slack or Zulip for a chance to weigh in on new registrations.

So let’s not focus on the package name here and just congratulate @mnemnion for a package with some very nice functionality!

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<div class="post-metadata">

**Author:** ![rafael.guerra](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rafael.guerra/32/216610_2.png) [@rafael.guerra](https://discourse.julialang.org/u/rafael.guerra)\
**Post date:** [March 28, 2024, 10:43am UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202/6 "2024-03-28T10:43:51Z")

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> [@goerz](#):
>
> Slack or Zulip

Sorry, I do not frequent these places.

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<div class="post-metadata">

**Author:** ![goerz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/goerz/32/3269_2.png) [@goerz](https://discourse.julialang.org/u/goerz)\
**Post date:** [March 28, 2024, 10:46am UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202/7 "2024-03-28T10:46:46Z")

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That’s fine, but once a package is registered, the name is pretty much a done deal. Registered packages cannot really be renamed, although the author could decide to re-release the package under a new, different name. That kind of renaming is something that should be pretty rare, though, IMO.

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**Author:** ![aplavin](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/aplavin/32/222056_2.png) [@aplavin](https://discourse.julialang.org/u/aplavin)\
**Post date:** [March 28, 2024, 10:48am UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202/8 "2024-03-28T10:48:13Z")

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Looks cool despite some quirks!  
I wonder if there are packages implementing this approach to strings in other languages?

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<div class="post-metadata">

**Author:** ![mnemnion](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mnemnion/32/206596_2.png) [@mnemnion](https://discourse.julialang.org/u/mnemnion)\
**Post date:** [March 28, 2024, 5:28pm UTC](https://discourse.julialang.org/t/ann-stringunits-jl/112202/9 "2024-03-28T17:28:00Z")

</div>

> [@goerz](#):
>
> once a package is registered, the name is pretty much a done deal. Registered packages cannot really be renamed, although the author could decide to re-release the package under a new, different name.

Thank you. I’d like to point people to the original thread, `StringIndex` is @StefanKarpinski 's idea, and `StringUnits` is different enough that I didn’t want to arrogate the name.

> [@\_bernhard](#):
>
> Nice package!

Thanks!

> [@\_bernhard](#):
>
> while I see your point on the similarity to regular units, I think where the comparison to meters fails is that there is no fixed conversion factor between chars, graphemes, codepoints.

This is true! Let me point you to a quote in the documentation:

> A few of you are squirming in your chairs at this point. Yes, ‘addition’ of heterogeneous `StringUnits` doesn’t commute. Yes, this is abuse of notation. Yes, I’m interested in your breakdown of the real analysis of StringUnit metrics, including a notation. No, I won’t change StringUnits to use it. Yes, I would more-than-likely link to your contribution.

If I named the package `StringMetrics`, that would confuse almost everyone. Metrics can be associated with a unit, and while in physics care is taken to keep _standard_ units convertible, in mathematics more broadly, it doesn’t work that way.

Consider a line drawn across a map. Two metrics might be “counties crossed” and “streets crossed”, which could be given units, so you could say “move two counties left” or “give me the third through the seventh street in the second county”. These would not be interconvertible either, but they would be units.

I don’t mind a bit of bikeshedding about the name! But I suspect we’ve hit the limit on what might be usefully said.

> [@aplavin](#):
>
> Looks cool despite some quirks!  
> I wonder if there are packages implementing this approach to strings in other languages?

I’m not aware of any. Julia’s multiplication-by-juxtaposition is pretty unusual, as is the powerful genericity and dispatch which let me add methods to `getindex` when the first argument is already well-defined for `Integer` and `UnitRange`. So being able to exactly say things like `str[1gr:5gr]`, no, I haven’t seen that.

Swift’s Character type is an extended grapheme cluster, which, presuming both Julia and Swift implement the Unicode standard correctly, should be identical to graphemes in Julia. The language makes it cheap and easy to work with these, at the cost of a somewhat opaque representation of some things: Swift has a String.Index which is an index to a specific character on a specific string, this is more like the `StringIndex` in the original thread and I believe it was the inspiration behind it. It’s all [rather complicated](https://docs.swift.org/swift-book/documentation/the-swift-programming-language/stringsandcharacters/), and Strings are also mutable.

Swift is the only language I know which chose to make graphemes the basic unit. It’s possible to get your hands on “Unicode scalar values”, what Julia calls a `Char`, but as far as I know, literal byte offsets (to codeunits) aren’t even available.

The quirks in `StringUnits` are really consequences of how Julia does intervals and indexing. So you need to keep in mind things like “second character after the fifth grapheme’s index” (5gr + 2ch) could be inside that grapheme, if it’s a long one like Farmer Bob here: 👨🏻‍🌾

I expect the only mixed units which will be particularly useful are a mixture of a native byte offset with one of the categories, things like `50 + 7gr`: the seven graphemes starting from index 50, which might come from `findfirst` or whatever.