Pretty printer for custom data types best practices?

Learning
5

the Genprint library uses the compilers’ type representation stored
in .cmt files to print.
it will print abstract types too from installed libraries as long as they
were compiled -bin-annot.
and here is an excerpt from the test file on creating a custom
printer for an abstract type:

  let open Bigarray in
  let open Array1 in
  let a1=create Float32 C_layout 1 in
  set a1 0 99.9;
  (* this is abstract because it resides at the C level *)
  [%pr bigarray abstracted a1];
  let a1print ppf (a1: _ Array1.t) = Format.fprintf ppf "got it...%f" (get a1 0) in
  (* %printer only accepts an identifier, not a closure *)
  [%install_printer a1print];
  (* now uses the printer *)
  [%pr bigarray unmasked a1];
  (* and the value directly *)
  [%pr bigarray content(get a1 0 )];
  (* and remove it... *)
  [%remove_printer a1print];
  [%pr bigarray abstract again a1];

the project repo also has a demo of the library integrated into the debugger.

nb. the availability of .cmt files is a runtime requirement, in-line
with the development focus of the library.