# binarySearchBy<K extends Comparable<K> > method

Returns the index of `element`

in this sorted list.

Uses binary search to find the location of `element`

.
This takes on the order of `log(n)`

comparisons.
The list *must* be sorted according to the natural ordering of
the `keyOf`

of elements, otherwise the result is unspecified.

Returns -1 if `element`

does not occur in this list.

If `start`

and `end`

are supplied, only the list range from `start`

to
`end`

is searched, and only that range needs to be sorted.

## Implementation

```
int binarySearchBy<K extends Comparable<K>>(
E element, K Function(E element) keyOf, [int start = 0, int? end]) =>
algorithms.binarySearchBy<E, K>(
this, keyOf, (a, b) => a.compareTo(b), element, start, end);
```