Hi all, Hoping for some casual coaching on basic printing of module types. I want to print instances of the following, writing as little of my own formatters as possible. module CharSet = Set.Make (Char) module CharMap = Map.Make (Char) In the Map case, clearly the value type is not speficified,…

I think the usual thing to do here is to convert your set/map to a list and then print that with [%derive.show: (char * value) list]

Thank you. I’m so glad I asked! module CharSet = Set.Make (Char) module Signals = CharSet (* snip *) print_endline @@ [%show: char list] (Signals.elements signals); Would be really slick if I could have print_endline @@ [%show: Signals.elt list] (Signals.elements signals); (* Unbound value Signal…

Will this work? module Signals = struct include Set.Make(Char) type nonrec t = t [@derive.show] type nonrec elt = elt [@derive.show] I may check it later

The containers stdlib extension makes this almost effortless: open Containers module Signals = Set.Make(Char) let () = Format.printf "my set: %a" (Signals.pp Char.pp) @@ Signals.of_list ['a'] “Almost”, because the pp on Set, Map, etc needs to be parameterized by the value in question; but you can…

Splendid. Containers tends to be my go-to stdlib ext, so this is particularly helpful for me :slight_smile:

@vrotaru , no, it’s explicitly not supported: Raise an error when `type nonrec` is encountered ocaml-ppx:master ← emillon:nonrec-raise-error opened 10:58AM - 21 Dec 16 UTC (UTC) [emillon] …

While nonrec is not supported, a type alias like this wouldn’t work since it would just generate an alias for the other printer. For example: type other = t [@@deriving show] will only add: let show_other = show let pp_other = pp To generate an actual definition, it needs access to the type defi…

Ppx_deriving implementation for pretty printing sets & maps

Learning

rgrinberg December 13, 2021, 2:17am 4

I suspect all we’re really missing is the Set/Map functors implementing pp functions. If we had that, you’d be able to use [%show: Signals.t].

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Ppx_deriving implementation for pretty printing sets & maps

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