# searchsortedlast

searchsortedlast(a, x, [by=,] [lt=,] [rev=false])

Returns the index of the last value in `a` less than or equal to `x`, according to the specified order. Returns `0` if `x` is less than all values in `a`.

## Examples

In the Julia programming language, the function `searchsortedlast(a, x, [by=<transform>,] [lt=<comparison>,] [rev=false])` is used to find the index of the last value in `a` that is less than or equal to `x`, based on the specified order. If `x` is less than all values in `a`, it returns `0`. Here are some examples of how to use this function:

1. Find the last value less than or equal to a given number:

``````julia> arr = [1, 3, 5, 7, 9];
julia> searchsortedlast(arr, 6)
3``````

In this example, the function returns the index `3` since it is the last index where the value is less than or equal to `6`.

2. Use a custom comparison function:

``````julia> arr = ["apple", "banana", "grape", "orange"];
julia> searchsortedlast(arr, "pear", lt = (a, b) -> length(a) < length(b))
2``````

Here, the function uses a custom comparison function to determine the order based on the length of the strings. It returns the index `2` since it is the last index where the length of the value is less than the length of `"pear"`.

3. Perform a reverse search:
``````julia> arr = [5, 4, 3, 2, 1];
julia> searchsortedlast(arr, 3, rev = true)
3``````

In this example, the function performs a reverse search and returns the index `3` since it is the last index where the value is less than or equal to `3` in the reversed array.

Common mistake example:

``````julia> arr = [1, 3, 5, 7, 9];
julia> searchsortedlast(arr, 10)
0``````

In this example, the value `10` is greater than all the values in the array `arr`. Therefore, the function returns `0` as specified in the function's behavior when `x` is less than all values in `a`.