# max(by:)

Returns the maximum element in the sequence, using the given predicate as the comparison between elements.

`@warn_unqualified_access func max(by areInIncreasingOrder: (Self.Element, Self.Element) throws -> Bool) rethrows -> Self.Element?`

## Parameters

- areInIncreasingOrder
A predicate that returns

`true`

if its first argument should be ordered before its second argument; otherwise,`false`

.

## Returns

The sequenceâ€™s maximum element if the sequence is not empty; otherwise, `nil`

.

## Overview

The predicate must be a *strict weak ordering* over the elements. That is, for any elements `a`

, `b`

, and `c`

, the following conditions must hold:

`areInIncreasingOrder(a, a)`

is always`false`

. (Irreflexivity)If

`areInIncreasingOrder(a, b)`

and`areInIncreasingOrder(b, c)`

are both`true`

, then`areInIncreasingOrder(a, c)`

is also`true`

. (Transitive comparability)Two elements are

*incomparable*if neither is ordered before the other according to the predicate. If`a`

and`b`

are incomparable, and`b`

and`c`

are incomparable, then`a`

and`c`

are also incomparable. (Transitive incomparability)

This example shows how to use the `max(by:)`

method on a dictionary to find the key-value pair with the highest value.

```
let hues = ["Heliotrope": 296, "Coral": 16, "Aquamarine": 156]
let greatestHue = hues.max { a, b in a.value < b.value }
print(greatestHue)
// Prints "Optional((key: "Heliotrope", value: 296))"
```