---
title: "elementsEqual(_:by:)"
framework: swift
role: symbol
role_heading: Instance Method
path: "swift/joinedsequence/elementsequal(_:by:)"
---

# elementsEqual(_:by:)

Returns a Boolean value indicating whether this sequence and another sequence contain equivalent elements in the same order, using the given predicate as the equivalence test.

## Declaration

```swift
func elementsEqual<OtherSequence>(_ other: OtherSequence, by areEquivalent: (Self.Element, OtherSequence.Element) throws -> Bool) rethrows -> Bool where OtherSequence : Sequence
```

## Parameters

- `other`: A sequence to compare to this sequence.
- `areEquivalent`: A predicate that returns true if its two arguments are equivalent; otherwise, false.

## Return Value

Return Value true if this sequence and other contain equivalent items, using areEquivalent as the equivalence test; otherwise, false.

## Discussion

Discussion At least one of the sequences must be finite. The predicate must be an equivalence relation over the elements. That is, for any elements a, b, and c, the following conditions must hold: areEquivalent(a, a) is always true. (Reflexivity) areEquivalent(a, b) implies areEquivalent(b, a). (Symmetry) If areEquivalent(a, b) and areEquivalent(b, c) are both true, then areEquivalent(a, c) is also true. (Transitivity) note: O(m), where m is the lesser of the length of the sequence and the length of other.