Fwd: Raw string literals: learning from Swift

Brian Goetz brian.goetz at oracle.com
Fri Jan 11 19:16:10 UTC 2019

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> Begin forwarded message:
> From: Fred Curts <fred.curts at icloud.com>
> Subject: Raw string literals: learning from Swift 
> Date: January 11, 2019 at 2:15:10 PM EST
> To: amber-spec-comments at openjdk.java.net
> With Swift 5 recently adding custom String delimiters (also called raw string literals), I find the design of Swift's string literals very compelling, more so than other languages I've studied.
> https://github.com/apple/swift-evolution/blob/master/proposals/0200-raw-string-escaping.md <https://github.com/apple/swift-evolution/blob/master/proposals/0200-raw-string-escaping.md> (implemented in Swift 5)
> https://github.com/apple/swift-evolution/blob/master/proposals/0168-multi-line-string-literals.md <https://github.com/apple/swift-evolution/blob/master/proposals/0168-multi-line-string-literals.md> (implemented in Swift 4)
> https://docs.swift.org/swift-book/LanguageGuide/StringsAndCharacters.html#ID286 <https://docs.swift.org/swift-book/LanguageGuide/StringsAndCharacters.html#ID286>
> Here is what I like about Swift's string literals. In no particular order:
> 1. Multi-line and raw string literals are orthogonal features.
> (Try adding a literal dollar sign to a Kotlin multi-line string literal and you'll know what I mean.)
> 2. Custom string delimiters solve all the use cases for raw string literals but nevertheless support escape sequences and interpolation expressions.
> I've personally come across this need many times when trying to build larger regular expressions or code snippets out of smaller ones.
> 3. Escape sequences and interpolation expressions use the same escape character.
> This simplifies matters considerably, in particular once custom string delimiters are added to the mix.
> (Having multiple custom escape characters would be too much.)
> 4. Multi-line string literals are delimited by triple double quotes.
> This makes them visually compatible with but heavier than single-line string literals, which seems like a good fit.
> Distinct delimiters for single-line and multi-line string literals seem like a win for both humans and parsers.
> For example, it's easy to tell where the missing end quote of a single-line string literal belongs.
> 5. It's easy to control line indentation of multi-line string literals and leading and trailing whitespace of the entire string.
> All of this is settled at compile time.
> 6. Opening and closing delimiters of multi-line string literals must be on their own line.
> This avoids headaches with edge cases such as string literals ending with two double quotes.
> 7. Multi-line string literals with custom string delimiters can contain arbitrarily long sequences of double quotes.
> I hope I've convinced you that the design of Swift's string literals is worth a closer look.
> -Fred

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