Syntax

	$start.recursion($fun)

$start.recursion($fun, $min-depth, $max-depth)

Description

Creates a list by applying the function fun to each element of the set start and recursively to all its function results. The recursion ends when the function null, or a previous result is regenerated. Only the elements resulting from recursion depths between min-depth (inclusive) and max-depth (exclusive) are returned in the evaluation result.

Parameter

Name	Type	Description	Mandatory	Default
start	number/string/boolean/business object/set	The start value, or the start values of the recursion if specified in a set.	yes
fun	Function	A function to be executed recursively on start and the resulting results.	yes
min-depth	Number	The minimum recursion depth (inclusive).	no	0
max-depth	Number	The maximum recursion depth (exclusive).	no	-1 (infinite)

Return value

Type: Set

A set consisting of start and all function results from a minimum to a maximum recursion depth.

Examples

Count up

	1.recursion(x -> $x + 1, 0, 9)

Output: A set with values [1, 2, 3, 4, 5, 6, 7, 8, 9].

Starting from 1, the function that increments a value by 1 is applied 9 times. All results are returned in the result list.

Note: The same result can be achieved much easier and more efficiently using the expression count(1, 10), see Count.

Paths

	$x.recursion(node -> $node.get(`my:Type#parent`), 1)

Output: The path starting from an element in the variable x to the root of a tree along the parent attribute my:Type#parent.

The path starts with the direct parent of x. The value of x is not itself included in the path because the minimum depth (number of function applications) is set to 1.