SE-0354: Regex Literals

YOCKOW · April 28, 2022, 11:53pm

Sorry, but let me claim it again.

General remarks about bare /.../ :

I guess the reason why some people support /.../ is because "we have seen it in other languages" .
However, we have to remember that Swift is different from other languages in many senses.

First, (as mentioned repeatedly in this thread,) we can define prefix/infix/postfix operators containing / .
Authors simply think it is enough to change the syntax rule of Swift, but the fact that certain number of projects will be broken has come to light.

Second, regex in Swift may differ from ones in other languages.
Although this is out of scope of this pitch, it is related still.

Declarative String Processing Overview

When applied with grapheme-cluster semantics (the default if applied to String ), it would match grapheme-cluster by grapheme-cluster and comparison obeys canonical equivalence. There are some features that might not be supported, e.g. generalizing some scalar properties to grapheme clusters. Resulting indices would be grapheme-cluster aligned.

Such feature would confuse some folks especially from other languages.
Let me quote my opinion from pitch#1 thread:

[Pitch] Regular Expression Literals

My thoughts are

If Swift adopts similar literals with e.g. Perl, semantics should be similar with Perl.

If Swift adopts different semantics from e.g. Perl, literals should be different from Perl.

That would be called perceived affordance.

Lastly, Swift has sublime philosophy (I hope).
I agree that /.../ is simple and easy to write.
However, to be simple is not enough to be good in Swift.
I want to quote Mr. Lattner's utterance:

`if let` shorthand

The goal of Swift language design isn't to minimize number of characters in code, it is to find a balance between "expressivity", and "readability". Readability isn't just "what does this line of code do" it is a deeper "what is the lifecycle of maintaining and evolving a codebase, particularly when it is worked on by multiple people, or the project spans years of development".

/.../ will certainly break Swift.
/.../ is not Swift's.
Does Swift have to borrow the syntax from others to break itself?
Will we get more benefit from /.../ than loss from it?
Think different.