Index of substring in string?

[xwu (Xiaodi Wu)]

See this very useful explainer:

Why are String offsets so complicated?

Others have addressed various reasons for why Swift doesn't do this, but I want to highlight why making this "just work" is not necessarily a practical solution, from a very realistic standpoint. Human text is incredibly complex, and the details are very intricate. @Michael_Ilseman can corroborate (or refute) what I have to say here, but let's explore taking an approach of making String indexing O(1) to the end might entail. To begin with, I'd like to point out that Unicode off the bat allows f…

I'll point out specifically this excerpt:

I'll echo what @jrose said above — very often, the use cases I've seen for random access into String s have been pretty much contrived. It's extremely rare to need to actually jump around inside of a String and very often, by the time you're doing that, you're either not really benefitting from the semantic correctness that String offers, or you really need a different data structure.