Why is ♡ a Math char but not an Emoji?

[LuckyTurtleDev]

Why is ♡ a Math char but not an Emoji?

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=392c54b54c6046997283bbe6824bd079

[BurntSushi]

♡ corresponds to U+2661.

Why is ♡ a Math char

Because of this line

2660..2663    ; Math # So   [4] BLACK SPADE SUIT..BLACK CLUB SUIT

in DerivedCoreProperties.txt provided by the Unicode consortium.

not an Emoji?

Becuase U+2661 isn't listed as an Emoji in the emoji data provided by the Unicode consortium. It is listed as Extended_Pictographic though:

2661..2662    ; Extended_Pictographic# E0.0   [2] (♡..♢)    WHITE HEART SUIT..WHITE DIAMOND SUIT

---

Overall, this is not a question for the regex engine. It's a question for the Unicode consortium. Moreover, I suspect this is an instance of the XY problem. I note that \p{Emoji} does not match every possible thing that a human thinks of as an "emoji." It couldn't possibly because character classes can only match a single codepoint. An emoji, however, can be a sequence of many codepoints. From the looks of it, you appear to have been misled by ihateregex.io. That comes as no surprise to me.

The correct definition of emoji comes from UTS#51. It is a lot more complicated than, "an emoji is a finite set of codepoints." I don't know whether you can use a regex to match emoji or not.

The fundamental issue here is that \p{Emoji} is poorly named. It is actually a lower level implementation detail of what makes up a proper "emoji." But given its name, it looks like it's the thing you want. It isn't. It needs to be combined with other stuff.

See also:

• why doesn't \p{Emoji}+ match all emoji? #947
• Emoji group matches digits #704
• How to I find all occurences of emojis in my codebase? BurntSushi/ripgrep#1623 (comment)

[LuckyTurtleDev]

thanks for the fast and comprehensive answer