What ⌸ means
It groups values by key, then applies a function to each group.
APL is a language for working with arrays, ordered collections of values. In X f⌸Y, entries in X key corresponding entries in Y; f processes each group. Results follow first-seen key order.
J documented related notation x u/. y by November 1991. Dyalog APL introduced ⌸ in 2013; its Classic Edition used ⎕U2338 as the textual form.
Don't confuse it with
1Questions people ask
1Why does ⌸ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type ⌸
Windows (Word)
Alt+XType 2338, then Alt+X to get ⌸.
Windows
Win+Rrun charmap for the full table, or use the emoji picker's Ω symbols tab (Win + .).
macOS
Control+Command+SpaceOpen the character viewer and search “apl functional symbol quad equal”.
Linux
Ctrl+Shift+UType 2338, then Enter or Space.
HTML
⌸CSS
\2338How to type ⌸
Use an APL keyboard layout with customizable modifier-key mappings, or Dyalog 18.2’s Unicode input method editor (IME).
Codes and encoding1 code points
HTML decimal
⌸
HTML hex
⌸
CSS content
content: "\2338";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%8C%B8
1
On screen
1
Code points
1
JS .length
3
UTF-8 bytes
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.