Data structures overview

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

q provides the following data structures:

Name	Nr of Elements	Definition	Example
Atom	\(1\)	A single, indivisible value of a specific type.	3.14
List	\(n \times 1\)	An ordered, zero-indexed sequence of values of uniform or mixed type, also called an array.	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 list of conforming dictionaries.	([] 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	Nr of Elements	Definition	Example
Table dictionary	\(\left(\sum_{i=1}^{s} n_i\right) \times m\)	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))