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# BoxSetFilter

Return a new Set containing only the elements of the source Set for which the predicate returns true.

The result is a new Set of the same variant as the source; the source is not modified. The predicate receives the element value, its 1-based ordinal position, and the Set itself.

## Method Signature

```
BoxSetFilter(set=[set], callback=[function:Predicate])
```

### Arguments

| Argument   | Type                 | Required | Description                                                                                                                                                    | Default |
| ---------- | -------------------- | -------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
| `set`      | `set`                | `true`   | The set to filter.                                                                                                                                             |         |
| `callback` | `function:Predicate` | `true`   | <p>Predicate invoked for each element. Receives {@code (value, ordinal, set)}.<br>Elements for which this returns {@code true} are included in the result.</p> |         |

## Examples

### Keep only elements that satisfy a predicate

Returns a new Set containing elements for which the callback returns `true`.

```java
s = [ 1, 2, 3, 4, 5 ].toSet();
evens = s.filter( ( Any v ) => v % 2 == 0 );
writeOutput( evens.size() );

```

Result: 2

### Filter strings by length

```java
s = setOf( "cat", "elephant", "ox", "deer" );
long = s.filter( ( Any v ) => len( v ) > 3 );
writeOutput( long.size() );

```

Result: 2

## Related

* [BoxSetAdd](/boxlang-language/reference/built-in-functions/set/boxsetadd.md)
* [BoxSetAddAll](/boxlang-language/reference/built-in-functions/set/boxsetaddall.md)
* [BoxSetClear](/boxlang-language/reference/built-in-functions/set/boxsetclear.md)
* [BoxSetContains](/boxlang-language/reference/built-in-functions/set/boxsetcontains.md)
* [BoxSetContainsAll](/boxlang-language/reference/built-in-functions/set/boxsetcontainsall.md)
* [BoxSetDifference](/boxlang-language/reference/built-in-functions/set/boxsetdifference.md)
* [BoxSetEach](/boxlang-language/reference/built-in-functions/set/boxseteach.md)
* [BoxSetEquals](/boxlang-language/reference/built-in-functions/set/boxsetequals.md)
* [BoxSetEvery](/boxlang-language/reference/built-in-functions/set/boxsetevery.md)
* [BoxSetFind](/boxlang-language/reference/built-in-functions/set/boxsetfind.md)
* [BoxSetIntersection](/boxlang-language/reference/built-in-functions/set/boxsetintersection.md)
* [BoxSetIsDisjointFrom](/boxlang-language/reference/built-in-functions/set/boxsetisdisjointfrom.md)
* [BoxSetIsEmpty](/boxlang-language/reference/built-in-functions/set/boxsetisempty.md)
* [BoxSetIsSubsetOf](/boxlang-language/reference/built-in-functions/set/boxsetissubsetof.md)
* [BoxSetIsSupersetOf](/boxlang-language/reference/built-in-functions/set/boxsetissupersetof.md)
* [BoxSetMap](/boxlang-language/reference/built-in-functions/set/boxsetmap.md)
* [BoxSetNone](/boxlang-language/reference/built-in-functions/set/boxsetnone.md)
* [BoxSetReduce](/boxlang-language/reference/built-in-functions/set/boxsetreduce.md)
* [BoxSetReject](/boxlang-language/reference/built-in-functions/set/boxsetreject.md)
* [BoxSetRemove](/boxlang-language/reference/built-in-functions/set/boxsetremove.md)
* [BoxSetRemoveAll](/boxlang-language/reference/built-in-functions/set/boxsetremoveall.md)
* [BoxSetRetainAll](/boxlang-language/reference/built-in-functions/set/boxsetretainall.md)
* [BoxSetSome](/boxlang-language/reference/built-in-functions/set/boxsetsome.md)
* [BoxSetSymmetricDifference](/boxlang-language/reference/built-in-functions/set/boxsetsymmetricdifference.md)
* [BoxSetToArray](/boxlang-language/reference/built-in-functions/set/boxsettoarray.md)
* [BoxSetToList](/boxlang-language/reference/built-in-functions/set/boxsettolist.md)
* [BoxSetUnion](/boxlang-language/reference/built-in-functions/set/boxsetunion.md)
* [ObjectToSet](/boxlang-language/reference/built-in-functions/set/objecttoset.md)
* [SetNew](/boxlang-language/reference/built-in-functions/set/setnew.md)
* [SetOf](/boxlang-language/reference/built-in-functions/set/setof.md)
* [StructKeySet](/boxlang-language/reference/built-in-functions/set/structkeyset.md)
* [StructValueSet](/boxlang-language/reference/built-in-functions/set/structvalueset.md)
* [ToSet](/boxlang-language/reference/built-in-functions/set/toset.md)


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