Optional parameters: Difference between revisions

=={{header|OCaml}}==

OCaml has optional named parameters.

<lang ocaml>let sort_table ?(ordering = compare) ?(column = 0) ?(reverse = false) table =

let cmp x y = ordering (List.nth x column) (List.nth y column) * (if reverse then -1 else 1) in

List.sort cmp table</lang>

Example uses:

<lang ocaml># let data = [["a"; "b"; "c"]; [""; "q"; "z"]; ["zap"; "zip"; "Zot"]];;

val data : string list list =

[["a"; "b"; "c"]; [""; "q"; "z"]; ["zap"; "zip"; "Zot"]]

# sort_table data;;

- : string list list =

[[""; "q"; "z"]; ["a"; "b"; "c"]; ["zap"; "zip"; "Zot"]]

# sort_table ~column:2 data;;

- : string list list =

[["zap"; "zip"; "Zot"]; ["a"; "b"; "c"]; [""; "q"; "z"]]

# sort_table ~column:1 data;;

- : string list list =

[["a"; "b"; "c"]; [""; "q"; "z"]; ["zap"; "zip"; "Zot"]]

# sort_table ~column:1 ~reverse:true data;;

- : string list list =

[["zap"; "zip"; "Zot"]; [""; "q"; "z"]; ["a"; "b"; "c"]]

# sort_table ~ordering:(fun a b -> compare (String.length b) (String.length a)) data;;

- : string list list =

[["zap"; "zip"; "Zot"]; ["a"; "b"; "c"]; [""; "q"; "z"]]</lang>