How does one print any type?

Learning
3

You may also use the ppx_deriving.show plugin from the ppx_deriving library. This plugin is able to generate 'a -> string and Format.formatter -> 'a -> unit (where 'a is the type you want to print) functions which can then be used for value printing.

type t =
{  number : int
;  text : string
}[@@deriving show]

This will produce show and pp functions of type t -> string and Format.formatter -> t -> unit, which can then be used as

let v = { number = 2; text = "Hello world"} in
print_endline (show v)

or

let v = { number = 2; text = "Hello world"} in
let s = Format.asprintf "%a" pp v in
print_endline s

Of course, you can always define such functions for the needed types by yourself.

As I can see, almost every library introducing a new type also provides pretty-printing (kinda pp in this example) functions out of the box.

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