Editing OCaml (section)

=== Option ===
The <code>option</code> type constructor in OCaml, similar to the <code>Maybe</code> type in [[Haskell]], augments a given data type to either return <code>Some</code> value of the given data type, or to return <code>None</code>.<ref>{{Cite web |title=3.7. Options — OCaml Programming: Correct + Efficient + Beautiful |url=https://cs3110.github.io/textbook/chapters/data/options.html |access-date=2022-10-07 |website=cs3110.github.io}}</ref> This is used to express that a value might or might not be present.<syntaxhighlight lang="ocaml">
# Some 42;;
- : int option = Some 42
# None;;
- : 'a option = None
</syntaxhighlight>This is an example of a function that either extracts an int from an option, if there is one inside, and converts it into a [[String (computer science)|string]], or if not, returns an empty string:<syntaxhighlight lang="ocaml">
let extract o =
  match o with
  | Some i -> string_of_int i
  | None -> "";;
</syntaxhighlight><syntaxhighlight lang="ocaml">
# extract (Some 42);;
- : string = "42"
# extract None;;
- : string = ""
</syntaxhighlight>