Generic Instance Method


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.


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



A sequence to compare to this sequence.


A predicate that returns true if its two arguments are equivalent; otherwise, false.

Return Value

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


At least one of the sequences must be finite.

The predicate must be a equivalence relation over the elements. That is, for any elements a, b, and c, the following conditions must hold:

Complexity: O(m), where m is the lesser of the length of the sequence and the length of other.

  • 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)