reduce Statement

Reduces an array to a scalar value by recursively applying an expression to each array element and its next element.

Syntax	reduce anArray using <expression with element and nextElement> if single use <expression with element>
Semantics	reduce allows you to reduce an array having elements of base or complex types to a scalar value by recursively applying an expression to each array element and its next element. The array must exists and contain at least one element. element and nextElement are keywords and allow you to use relative references (as opposed to normal, absolute indexes) to single elements of an array, see Get Array Element Operator []). if single use is a mandatory extension and allows to define the action for an array containing only one single element. The strength of reduce is to efficiently perform calculations on array elements. String operations, however, are not very efficient, and may cause performance issues with big arrays.
Substitutables	anArray	Can be any variable or object attribute having the type Array.
	<expression with element and next element>	This expression must use the currently evaluated array element and its next neighbor and evaluates to a scalar having the same type as the result value.
	<expression with element>	The expression after if single use uses the sole array element and evaluates to a scalar having the same type as the result value.
Error Codes	FUMSM/9	The reduce function can only work on complex types.
	FUMSM/10	The first item of a reduce function is NULL.
	FUMSM/11	The reduce function returned NULL.
Examples	Concatenate all string elements of an array to a single string, separated by space Input: an array of names JSON {"names": ["Irene", "Eliza", "Raymond", "Jane", "David"]} CODE set result = reduce names using concat(element, " ", nextElement) if single use element; Result: result is “Irene Eliza Raymond Jane David".
	Get the overall length of all strings in an array Input: an array of names JSON {"names": ["Irene", "Eliza", "Raymond", "Jane", "David"]} CODE set result = reduce names using element.stringLength() + nextElement.stringLength() if single use element.stringLength(); Result: result is 26.
	Calculate a sum through all array elements Input: an array of a complex article JSON { "articles": [ {"name": "AF-1200", "category": "Adapter", "orderValue": 10,256.30}, {"name": "CD-2024", "category": "Connector", "orderValue": 9,563.78}, {"name": "RC-0002", "category": "Adapter", "orderValue": 162.55}, {"name": "CD-2002", "category": "Connector", "orderValue": 510.01} ]} CODE set result = reduce articles using element.orderValue + nextElement.orderValue if single use element.orderValue; Result: result is 20,492.64.

Some More Examples

Reducing Arrays with Elements of Complex Type

The same algorithm applies to arrays with elements of complex types as described above. Since each element or nextElement refers to an object of complex type, you can access the attributes of the object like any other instance (e.g. element.name).

Input: an array of a complex article

In the example below, array articles contains objects of complex type Article. You want to copy the name property of each array element to a single string separated by a comma.

{ "articles": [
    {"name": "AF-1200", "category": "Adapter", "serviceInterval": 52},
    {"name": "CD-2024", "category": "Connector", "serviceInterval": 208},
    {"name": "RC-0002", "category": "Adapter", "serviceInterval": 104},
    {"name": "CD-2002", "category": "Connector", "serviceInterval": 26}
]}

set result = reduce articles using concat(element.name, ", ", nextElement.name)
                    if single use element.name; 

Result: result is “AF-1200, CD-2024, RC-0002, CD-2002”.

Single Array Element

For arrays that contain only one single element, you can use the (mandatory) extension if single use in the reduce statement.

Input: an array of a complex article

Let’s enhance the previous example with a text.

{"articles": [
    {"name": "AF-1200", "category": "Adapter", "serviceInterval": 52}
]}

set result = reduce articles using concat(element.name, ", ", nextElement.name)
                    if single use concat("Single article: ", element.name);

Result: result is “Single article: AF-1200”.

If an array has only one single element, the statement following if single use will be evaluated.

Reduce Algorithm

The reduce algorithm works as follows: Suppose you want to sum up all elements of an array numbers containing the numbers 1, 2, and 3.

{"numbers": [1,2,3]}

set result = reduce numbers using element + nextElement
                            if single use element;

:1_one_square_blue: First iteration

1. The first occurrence of the element expression is initialized (here: take the first integer 1).

2. Then the next element is evaluated and added (+ nextElement, 2 in this example).

3. The result of the first iteration is 3.

:2_two_square_blue: Second iteration
Now, element refers to the intermediate result of the first iteration.

1. nextElement is added again, which is 3 in this example.

2. The resulting value is 6.

:3_three_square_blue: FinalizationThe final value is finally assigned to integer result.

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