Data Structures Overview

This page provides an overview of the core data structures in q, including their structure, dimensions, and typical usage.

In q, the following data structures exist:

Name	Nr of Elements	Definition	Example
Atom	\(1 \times 1\)	A single, indivisible value of a specific type.	3.14
List/Array	\(n \times 1\)	An ordered, zero-indexed sequence of values, which can be uniform or mixed type.	1 2 3
Dictionary	\(n \times 2\)	A key-value mapping that associates a list of keys with a list of values.	("Alice; "Bob"; "Mike")!30 25 43
Table	\(n \times m\)	A collection of named, equal-length columns stored as a flipped dictionary.	([] name:`Alice`Bob; age:30 25)
Keyed Table	\(n \times (k + m)\)	A dictionary mapping a table of key columns to a table of value columns.	([id:1 2] name:`Alice`Bob; age:30 25)

You can build custom data structures from the basic data structures:

Name	Dimension	Definition	Example
Table Dictionary	\(\sum^s_{i=1}= n_{i} \times m\)	A dictionary of tables, in which the key is a unique list and the values are tables (typically sorted by time)	(`u#`Alice`Bob)!(([] time: `s#08:01 16:28; event: `login`logoff); ([] time: `s#08:02 08:29 17:02; event: `login`alarm`logoff))