<Array>.Reduce (Function)

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Queue, stack, list and array management functions

Existing computations

Related examples

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Reduce (Function)

<Array>.Reduce (Function)

In french: <Tableau>.Agrège

Applies a computation to each element of a WLanguage array.

Example

arrValue is array of int = [1,2,3,4,5]
TheSum is integer
TheSum = arrValue.Reduce((Value, TheSum) => { RESULT Value + TheSum }, 0)

// Note: this example is for illustrative purposes; to find the sum of elements of an array,
// it is preferable to use the Sum function

Syntax

<Result> = <Array>.Reduce(<Operation to perform> [, <InitialValue>])

<Result>: Type corresponding to the result

Result of the requested reduce operation.

<Array>: WLanguage array

Name of Array variable to use. This array must be a one-dimensional array.

<Operation to perform>: WLanguage procedure

Name of WLanguage procedure to run. This procedure can be:
a global or local procedure,
an internal procedure.
It is also possible to directly use a lambda.

<InitialValue>: Optional parameter, type corresponding to the initial value

Initial value to use the first time the <Operation to perform> procedure is run.

Remarks

Operating mode

The <Operation to perform> procedure is called a first time with two parameters:

the first element of the array,
the initial value specified with <Initial value>.

The procedure is then called for all other elements of the array with two parameters:

the element of the array,
the value returned by the previous call.

Illustrative example
Let's study the following example:

arrValue is array of int = [1,2,3,4,5]
TheSum is int
TheSum = arrValue.Reduce((Value, TheSum) => { RESULT Value + TheSum }, 0)

In this example, the code:

TheSum = arrValue.Reduce((Value, TheSum) => { RESULT Value + TheSum }, 0)

is equivalent to the following code:

TheSum = arrValue.Reduce(Add, 0)

INTERNAL PROCEDURE Add(Value, Total)
RESULT Value + Total
END

With this internal procedure, the calculation can be broken down as follows:

IntermediateResult1 = Add (t[1], InitialValue): in the example Add( 1, 0 ) -> 1
IntermediateResult2 = Add (t[2], IntermediateResult1): in the example Add( 2, 1 ) -> 3
...

Note: this example is for illustrative purposes; to find the sum of elements of an array, it is preferable to use <Array>.Sum.

Existing computations

The most common computations are available in WLanguage:


Versions 17 and later <Array>.Average New in version 17 <Array>.Average <Array>.Average	Calculates the mean of several elements: elements found in an array, numeric values, ...
Versions 17 and later <Array>.Sum New in version 17 <Array>.Sum <Array>.Sum	Calculates the sum of the array elements.

Related Examples:

Unit examples (WINDEV): Filter / Map / Reduce

[ + ] This example shows how to use the Filter / Map / Reduce functions.
The Filter / Map / Reduce concept allows performing operations on sets of data in a remarkably concise way.
Filter is used to filter an array of elements in a customized way (with a callback procedure).
Map is used to transform an array of elements, also with a callback procedure.
Reduce is used to aggregate data in a customized way with a callback procedure.
Here, this example is used to calculate the average age of women among the users displayed in the table below.

Business / UI classification: Neutral code

Component: wd260vm.dll