[stdlib] IntRange substring functions as get operators

[JordanLongstaff]

Not a huge motivation for this, call it syntactic sugar. I just don't know why this doesn't already exist.

[kotlin-safe-merge]

Code Owners

Rule	Owners	Approval
/​libraries/​stdlib/​	@DmitryNekrasov, @fzhinkin, @ilya-g, @qwwdfsad	❌

[lppedd]

This gets very awkward. Pretty much every developer in every language is used to either indexed access (str[index]) to get a single character, or to str.substring(start, end) for a piece of a string. Introducing a "fake" indexed access with a range is both confusing and error prone, but that's just my opinion.

[JakeWharton]

Pretty much every developer in every language is used to either indexed access (str[index]) to get a single character, or to str.substring(start, end) for a piece of a string.

Python:

'hello, world'[1:6]

Rust:

let a = "hello, world";
let b = &a[1..6];

Ruby:

"hello, world"[1..6]

C#:

"hello, world"[1..6]

Julia:

"hello, world"[1:6]

and on…

[lppedd]

The literal form is probably fine and understandable. However once you extract the range into a separate variable it loses most of its sense and readability.

[JakeWharton]

Do you also switch to invoking the named function when your indexing value changes from a literal to a variable?

It's just a variable naming problem.

[lppedd]

Index access has been there forever, so that point doesn't really make a lot of sense imo.
Kotlin's goal is to prioritize readability. But I'm obviously not here to block useful features if the community feels the need for them. I personally don't like expanding the (already quite large) standard library with non-critical missing features.

[JakeWharton]

I'm not sure what the age of the capability has to do with it. You claimed that when one transition's from a literal to a variable that the special syntax no longer makes sense and the named function should be used.

However once you extract the range into a separate variable it loses most of its sense and readability.

Surely that holds true for plain indexing then, too?

[lppedd]

I'm not sure what the age of the capability has to do with it

When you see str[whatever] it is obvious we're talking about getting a single character at whatever index.
Introducing these two functions means whatever might be a range, and you're actually getting a substring. Code you read and understood yesterday might not have the same meaning anymore.

[kshulzh]

Hi all, what about this option?
public inline operator fun String.get(start: Int, end: Int): String = substring(start, end)
usage
val hello ="Hello World"[0,5]
`