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better documentation for string reversal #23793

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Sep 21, 2017
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better documentation for string reversal #23793

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better documentation for string reversal
stevengj Sep 20, 2017
fcd74c8
Update types.jl
stevengj Sep 20, 2017
5459078
Update types.jl
stevengj Sep 20, 2017
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15 changes: 14 additions & 1 deletion base/strings/types.jl
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Expand Up @@ -117,10 +117,23 @@ end

Reverses a string.

Technically, this function reverses the "codepoints" in a string, and its
main utility is for reversed-order string processing, especially for reversed
regex (regular expression) searches. See also [`reverseind`](@ref) to convert indices
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Just "regular expression"? Also, which use quotes around "codepoints"?

in `s` to indices in `reverse(s)` and vice-versa, and [`graphemes`](@ref)
to operate on user-visible "characters" (graphemes) rather than codepoints
(which is more [visually pleasing but less useful](https://github.com/JuliaLang/julia/issues/6165) for reverse searching).
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I wouldn't refer to GitHub issues in the official docs. Anyway people are unlikely to use graphemes unless they have a reason to, given that it's easier to iterate over/reverse codepoints.


# Examples
```jldoctest
julia> reverse("JuliaLang")
"gnaLailuJ"

julia> reverse("ax̂e") # combining characters can lead to surprising results
"êxa"

julia> join(reverse(collect(graphemes("ax̂e")))) # reverses graphemes
"ex̂a"
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@stevengj stevengj Sep 20, 2017 •
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The hat is shown in the wrong place in github's diff display in by browser, but if I paste it into my terminal it is correct. Apparently their display of combining characters is broken?

github:
image

copy/paste from github into a Julia session in a terminal:
image

copy/paste from github into Atom:
image

```
"""
reverse(s::AbstractString) = RevString(s)
Expand All @@ -131,7 +144,7 @@ reverse(s::RevString) = s.string
"""
reverseind(v, i)

Given an index `i` in `reverse(v)`, return the corresponding index in `v` so that
Given an index `i` in [`reverse(v)`](@ref), return the corresponding index in `v` so that
`v[reverseind(v,i)] == reverse(v)[i]`. (This can be nontrivial in the case where `v` is a
Unicode string.)
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BTW, "Unicode string" is a weird terminology since now all strings support Unicode. Maybe just remove that sentence? Or say that it's nontrivial because of non-ASCII characters.


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