Change second argument of str.substring to accept length, not second index

[Chriscbr]

Use Case

Feedback from @eladb and @olivernybroe

Proposed Solution

No response

Implementation Notes

No response

Component

SDK

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[Chriscbr]

I'm not sure if there's a "right" API here. I was curious what other languages do, here's what I found:

• Kotlin - substring method accepts start and end index (https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/substring.html)
• Rust - no substring method, but you can do s[3..6] on a string slice
• Swift - no substring method, but they have subscript() which accepts a range (pair of indices) (https://developer.apple.com/documentation/swift/string/subscript(_:)-2so14)
• Golang - no substring method, but you can do s[3..6] on an ASCII string (https://stackoverflow.com/questions/61353016/why-doesnt-golang-have-substring)
• C# - substring method accepts start index and length (https://learn.microsoft.com/en-us/dotnet/api/system.string.substring?view=net-8.0#system-string-substring(system-int32-system-int32))
• JavaScript - substring method accepts start and end index (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substring)
• Python - no substring method, but you can do s[3..6] on strings
• PHP - substring method takes start index and length (https://www.php.net/manual/en/function.substr.php)
• Ruby - no substring method, but slice() can accept a start index and length or a range (https://ruby-doc.org/3.2.2/String.html)
• Dart - substring method takes start and end index (https://api.dart.dev/stable/3.2.4/dart-core/String/substring.html)

Personally I'm okay with either semantics. I've opened a separate issue for a dedicated string slicing syntax (s[3..6]): #5452

[eladb]

Thanks for the research!

Beautifully, JavaScript also has a substr method which accepts index and length, but it's deprecated.

Which makes me think that we should either stick with what we have right now to be compatible with modern JS, rename our method to substr or use keyword arguments to make this explicit:

s.substring(6, len: 2);

But maybe that's too much?

Also, slices ❤️

At any rate- Chris it's your call.