Function

a!flatten( array )

Converts an array that contains other arrays into an array of single items.

Parameters

Returns

Any Type Array

Usage considerations

Understanding results

a!flatten() removes nesting from arrays, such as those created by looping functions. When passed a simple array, a!flatten() returns it unmodified.

Nulls are not removed from lists. Use reject() and isnull() to easily remove nulls from a flattened list.

a!flatten() always returns an array, so when passed a single item, a!flatten() returns an array containing that item.

When passed an empty or null array, a!flatten() returns an empty array.

If the passed array is type Any Type, a!flatten() returns an array of the appropriate type.

Examples

Remove nesting from arrays

a!forEach(items: {1, 2, 3}, expression: enumerate(fv!item)) returns a 3 item list consisting of {0}, {0, 1}, and {0, 1, 2}

a!flatten(a!forEach(items: {1, 2, 3}, expression: enumerate(fv!item))) returns {0, 0, 1, 0, 1, 2}

Remove only array nesting

Only array nesting is removed when using a!flatten. Nested maps, dictionaries, and data types retain their structure.

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a!flatten(
  {
    a!map( id: 1 ),
    a!map( id: 2 ),
    a!map( id: 3, address: a!map( street: "Main Street", number: 101 ) )
  }
)

returns:

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{
  a!map( id: 1 ),
  a!map( id: 2 ),
  a!map( id: 3, address: a!map( street: "Main Street", number: 101 ) )
}

Retaining data types

typename(typeof(a!flatten({a: {1, 2, 3}}.a))) returns "List of Number (Integer)"

typename(typeof(a!flatten({a: {1, 2, "apple"}}.a))) returns "List of Variant"