Key

An accessor tag — At(assoc, Key(k)) looks up the value for key k in an Association.

✓ checked against that system · ! checked, with disagreements (hover a chip)Wolfram LanguageKey!↗

Key(k)an inert tag around k, meaningful as the second operand of At on an Association

Typed signatures

Type	Package	Applies
(any) -> any	combinatorics	always

Domain: Collections

Details

• Reads the SAME Rule-pair Association AssociationThread and list-functional.ts's Association build — not compute-engine's own string-keyed Dictionary.
• Missing(k) answers Missing rather than leaving the call unevaluated, matching Wolfram's own default.
• Wolfram's OTHER reading of Key — as a standalone operator, Key(k)(assoc) — isn't implemented; only the At(assoc, Key(k)) form is.

Examples

Basic #

live ↗

In$\mathrm{Association}(\mathrm{Rule}(a, 1), \mathrm{Rule}(b, 2))[\mathrm{Key}(b)]$Out$2$

Scope #

live ↗

In$\mathrm{Association}(\mathrm{Rule}(a, 1))[\mathrm{Key}(z)]$Out$\mathrm{Missing}$

About

Examples	2
Checked against	Wolfram Language 1 agree1 differ
Crosswalk	Wolfram Language

See also: AssociationThread, At