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 to each member of the collection and returns a new collection of the same type containing only those elements for which the lambda 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`	Collection	The target collection over which the `lambda` function iterates/operates.
`lambda`	Lambda	The anonymous function to be executed which must return a boolean.

collection

Collection

The target collection over which the lambda function iterates/operates.

lambda

Lambda

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

Returns

A new collection with the elements of the collection which caused lambda to return true.

Examples

The query below iterates over the collection 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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