JMM’s notes on the

Compose Key

You can see a pretty big list at https://cgit.freedesktop.org/xorg/lib/libX11/plain/nls/en_US.UTF-8/Compose.pre.

Math

See the XCOMM Characters from "Mathematical Operators" section of the compose key list. Also check out the section on arrows and “XCOMM Latin-1 Supplement”.

SequenceResultComment
8 8 ∞ Infinity
: - ÷ Division sign
x x × Multiplication sign
- _ − MINUS SIGN, not to be confused with “-” (HYPHEN-MINUS).
Note: This doesn’t yet work for me. This works differently depending where it’s input. Like, it works in the Firefox address bar for me (on 2023-12-11) but not in Emacs.
1 4 ¼ One quarter or “Vulgar fraction one quarter”.
^ 1 ¹ Superscript 1.
_ 1 ₁ Subscript 1.
- > → Rightwards arrow
| ^ ↑ Upwards arrow
| v ↓ Downwards arrow.
= > ⇒ Rightwards double arrow

I can’t find ways to enter:

Misc

Some fractions are just entered with the numerator and denominator. For example, “¼” is entered using Compose 1 4. I can’t find a way to easily input a “FRACTION SLASH” (i.e. “⁄”) though.

SequenceResultComment
- - . – En dash
- - - — Em dash
space space “ ” No-break space (non-breaking space).
- - space “­” Soft hyphen, which is usually invisible expect when used for word-wrapping.
" < or < " “ Left double quote
" > or > " ” Right double quote
! ? ‽ Interrobang
. = • Bullet
o c © Copyright sign
( ) ) 🄯 Copyleft symbol
o r ® Registered sign
t m ™ Trademark sign
s ! § Section sign
p ! Paragraph/pilcrow sign
| - † Dagger
| = ‡ Double dagger

Emacs

Emacs has a compose key input method (called “compose”). Pretty handy along with activate-transient-input-method (C-x \) for entering accents.

Android

For Android-like operating systems, Unexpected Keyboard (https://github.com/Julow/Unexpected-Keyboard) has a compose key which I really like.

Where are compose sequences defined?