<Array>.Filter (Function)

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WLanguage

WLanguage functions

Standard functions

Queue, stack, list and array management functions

Array functions

Prefix syntax

Filter

Presentation

Example

Operating mode

Related examples

See also

<Array>.Filter (Function)

In french: <Tableau>.Filtre

Returns an array containing the elements of a source array for which a procedure returns True.

Example

// Retrieve an array with all the customers
arrCustomer is array of Customer

// Construct the array of customers a with negative account balance
arrCustomerNegativeBalance is array of Customer
arrCustomerNegativeBalance = arrCustomer.Filter(ACustomer => ACustomer.Balance<0)

// -> keep even numbers of an array
arr2 is array of int = [1, 2, 3, 4]
arr2 = arr2.Filter( X => IsEven(X))
// arr2 = [2, 4]

Syntax

<Result> = <Source array>.Filter(<Condition to check>)

<Result>: WLanguage array

Array that contains the elements of the <Source array> for which the <Condition to check> returns True.

<Source array>: WLanguage array

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

<Condition to check>: WLanguage procedure

Name of the WLanguage procedure to be executed for each element of the <Source array>. This procedure must return True or False.
This procedure can be:
a global or local procedure,
an internal procedure.
It is also possible to directly use a lambda procedure.

Remarks

Operating mode

The <Condition to check> procedure is called for each element of the array by passing this element as a parameter.

If the procedure returns True, the element from the source array is stored in the <Result> array.

Sequence of functions
You can use array functions in a sequence.
The following functions can be used in a sequence:

This sequence can be used as a source for a FOR ALL statement or it can end with one of the following functions:

Example:

gnMean = garrUser.Filter(cbFilter).Map(cbMap).Mean()

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.

Component: wd280vm.dll