# Module `Sek.Segment`

The module `Segment`

offers facilities for working with array segments. An array segment is a triple of an array, a start index, and a length.

`val is_valid : 'a segment -> bool`

`is_valid (a, i, k)`

determines whether the index`i`

and length`k`

define a valid segment of the array`a`

.`is_valid`

is*O(1)*.

`val is_empty : 'a segment -> bool`

`is_empty seg`

determines whether the array segment`seg`

is empty.

`val iter : direction -> 'a segment -> ('a -> unit) -> unit`

`iter direction seg f`

applies the function`f`

in turn to every element of the array segment`seg`

. The direction of iteration is dictated by the parameter`direction`

. If`seg`

is of the form`(a, i, k)`

, then`iter`

has complexity*O(k)*, excluding the cost of the calls to`f`

.

`val iter2 : direction -> 'a segment -> 'b segment -> ('a -> 'b -> unit) -> unit`

`iter2 direction seg1 seg2 f`

applies the function`f`

in turn to every pair of elements drawn synchronously from the the array segments`seg1`

and`seg2`

. The two segments must have the same size. The direction of iteration is dictated by the parameter`direction`

.`iter2`

has complexity*O(n)*, excluding the cost of the calls to`f`

, where*n*denotes the the size of the two segments.