# Substring function?

**URL:** https://discourse.julialang.org/t/substring-function/76675
**Category:** New to Julia
**Tags:** strings, unicode
**Created:** [February 18, 2022, 7:41am UTC](https://discourse.julialang.org/t/substring-function/76675 "2022-02-18T07:41:49Z")
**Posts on this page:** 1
**Showing post:** 22

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### Author: ![Sukera](https://avatars.discourse-cdn.com/v4/letter/s/ce7236/32.png) [@Sukera](https://discourse.julialang.org/u/Sukera)
#### Post date: [February 19, 2022, 7:52am UTC](https://discourse.julialang.org/t/substring-function/76675/22 "2022-02-19T07:52:55Z")

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> [@rogerkeays](#):
>
> **Iterators use codepoints, whereas ranges use byte indexes**. I see the need for byte indexing, but being new to the language, this idiosyncracy tripped me up. I expected to be working with codepoints all the way down unless explicitly converting into bytes.

As far as I understand, the reason for this is to be able to support invalid UTF-8 in `String` as well. It’s quite common to have some corrupted data that’s treated as a string. It’s usually seen as a strength to be able to do that - I wouldn’t call it a “idiosyncracy”.

You may also be interested in some of these previous discussions about various parts of the `String` type in julia:

- [How does Char get stored? - #3 by StefanKarpinski](https://discourse.julialang.org/t/how-does-char-get-stored/49366/3)
- [A Python rant about types - #3 by StefanKarpinski](https://discourse.julialang.org/t/a-python-rant-about-types/43294/3)

> [@rogerkeays](#):
>
> For example, in Java

Java is using UTF-16, right? The same problems mentioned in the two links above should apply as well, as it’s a variable length encoding like UTF-8. I don’t know how java would treat those bad encodings though. I think java works around this problem by just not having strings decompose into an iterator of `char` easily, which can get quite hairy to implement in a performant way (I can’t find the links to previous discussions about that though, sorry).

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