Filter

Filter( collection, lambda )

Filter( collection, lambda )

Filter( collection, lambda )

Filter( collection, lambda )

filter_expr( lambda, collection )

filter collection lambda

Filter( collection, lambda )

Filter( collection, lambda )

Description

The Filter function applies the lambda function to each member of the collection, which is an array or a set, and returns a new array containing only those elements for which the lambda function returns true.

Providing a lambda function which does not return a boolean results in an "invalid argument" error. If a page is passed, its decorated fields are preserved in the result.

Parameters

Argument Type Definition and Requirements

Argument	Type	Definition and Requirements
`collection`	Array or Set	The group of items over which the `lambda` function iterates/operates.
`lambda`	Lambda	The anonymous function to be executed, which must return a boolean.

collection

Array or Set

The group of items over which the lambda function iterates/operates.

lambda

Lambda

The anonymous function to be executed, which must return a boolean.

Returns

A new array that contains only the elements of the collection for which the lambda function returned true.

Examples

The query below iterates over the array containing the values 1, 2, 3, executing the lambda function for each value. The lambda function returns true if the Modulo 2 of the value is 0, otherwise it returns false.

curl https://db.fauna.com/ \
    -u fnAChGwBcAACAO70ziE0cfROosNJHdgBmJU1PgpL: \
    -d '{
          "filter": {
            "lambda": "i",
            "expr": { "equals": [ 0, { "modulo": [ { "var": "i" }, 2 ] } ] }
          },
          "collection": [ 1, 2, 3 ]
        }'

client.Query(
  Filter(Arr(1, 2, 3), i => EqualsFn(0, Modulo(i, 2))));

System.out.println(
  client.query(
    Filter(
      Arr(Value(1), Value(2), Value(3)),
      Lambda(
            Value("i"),
            Equals(Value(0), Modulo(Var("i"), Value(2)))
      )
    )
  ).get());

result, _ := client.Query(
    f.Filter(
        f.Arr{1, 2, 3},
        f.Lambda("i", f.Equals(0, f.Modulo(f.Var("i"), 2))),
    ),
)

fmt.Println(result)

client.query(
  Filter(Arr(1, 2, 3), Lambda { i => Equals(0, Modulo(i, 2)) }))

client.query(
  q.filter_expr(
    lambda i: q.equals(0, q.modulo(i, 2)),
    [1, 2, 3]
  ))

$client.query do
  filter [1, 2, 3] do |i|
    equals(0, modulo(i, 2))
  end
end

client.query(
    Filter(
        collection: Arr(1, 2, 3),
        with: { i in Equals(0, Modulo(i, 2)) }
    )
)

client.query(
  q.Filter([1, 2, 3], q.Lambda("i", q.Equals(0, q.Modulo(q.Var("i"), 2)))))
.then((ret) => console.log(ret));

HTTP/1.1 200 OK
{ "resource": [ 2 ] }

[ 2 ]

[2]

[2]

[ 2 ]

[ 2 ]

[ 2 ]

[ 2 ]

[ 2 ]

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