Structure the code in modules

Learning
,
1

Hello,

I have troubles in splitting my app into modules & submodules using dune.

Here is my current project tree (following this SO answer: ocaml - Running OUnit tests using dune - Stack Overflow ) :

├── dune
├── dune-project
├── booleanFormulae
│   ├── booleanFormulae.ml // begins with "open Types"
│   ├── booleanFormulae.mli // begins with "open Types"
│   ├── dune
│   ├── parser.ml // begins with "open Types"
│   └── types.ml
├── main.ml
├── test
│   ├── dune
│   └── test.ml

Here is the root dune file:

(executable
 (name main)
 (libraries BooleanFormulae))

Here is lib/dune:

(library 
    (name BooleanFormulae)
    (libraries angstrom)
    (preprocess (pps ppx_deriving.show ppx_deriving.ord)))

In the dune docs (Stanza Reference — Dune documentation), it is said

By default dune will use all the .ml/.re files in the same directory as the dune file.

So if I understand well, in the main.ml I should be able to open BooleanFormulae.Parser or
open BooleanFormulae.Types.
However, dune build main.exe complains:

File "main.ml", line 2, characters 5-27:
2 | open BooleanFormulae.Parser
         ^^^^^^^^^^^^^^^^^^^^^^
Error: Unbound module BooleanFormulae.Parser

Just referring to Parser in main.ml doesn’t work either.

What should I do? And is my project globally well structured?

2

Related I think:

in the test/test.ml, I cannot refer to the values in types.ml (included in the booleanFormulae.mli interface) [Unbound constructor …], but I can do it in the main.ml file.

Here is my test/dune:

(test (name test) (libraries BooleanFormulae ounit2))
3

I might be wrong, but the message is
“unbound module BooleanFormulae.Parser”, not “unbound module BooleanFormulae”
Can we see your booleanFormular.mli ?

But also, your library is called BooleanFormulae and your file is BooleanFormulae
I’ve had issues with first letter case sensitivity in the past, try to have them matching

4

Hi, thank you for trying to help. Change the case of my file to uppercase doesnt seem to get things better.

Here is my BooleanFormulae.mli:

open Types

type decTree = DecLeaf of bool | DecRoot of string * decTree * decTree
module VarsSet :
sig
(* set signature *)
end

val getVars : tformula -> VarsSet.t
type env 
val empty_env : env
val env_of_bindings : (string * bool) list -> env
val evalFormula : env -> tformula -> bool
val buildDecTree : tformula -> decTree

type bddGraph

val buildBdd : tformula -> bddGraph
val isTautology : tformula -> bool
val areEquivalent : tformula -> tformula -> bool
module Dot :
sig

  type style = Red | Dashed | Bold
  type elt = Node of (int * string) | Vertex of (int * int)

  type digraph

  val empty : digraph
  val join : digraph -> digraph -> digraph
  val addWithStyle : elt -> style list -> digraph -> digraph
  val add : elt -> digraph -> digraph
  val join_in_bracket : string list -> string
  val show : string -> digraph -> string
end
val bddToDot : bddGraph -> Dot.digraph
val decTreeToDot : int -> decTree -> int * Dot.digraph
5

Ah ! I understand what’s happening now
Didn’t read your tree properly

When you have a file in your directory that has the same name as your library (booleanFormulae here), dune creates a library from this file.
Meaning, in booleanFormulae.ml you need:

module Parser = Parser

and in your booleanFormulae.mli you need

module Parser : sig
...
end
2 Likes
6

Thank you, problem solved for the BooleanFormulae.Parser. I still have an issue with the tests:

$ dune runtest
File "test/test.ml", line 4, characters 9-12:
4 | let p1 = Var "P1"
             ^^^
Error: Unbound constructor Var

(Var is one of the constructors of tformula which is defined in booleanFormulae/types.ml. It is however accessible in main.ml)

7

Does it work if you prefix the constructor with its module name: BooleanFormulae.Types.Var?

8

Careful, open != include, in your mli you open Types, but you don’t include it, so it will not be exported
Unless you fixed it afterwards ?

9

Thank you @yawaramin, but it doesn’t fix the issue…

@giltho I’ve tried to include Types instead of open Types in booleanFormulae.mli, but I have an “unbounded module type Types”:

File "BooleanFormulae/booleanFormulae.mli", line 2, characters 8-13:
2 | include Types
            ^^^^^
Error: Unbound module type Types
10

include Types doesn’t work but open Types does ? that doesn’t sound right

11

I think it would be helpful if you could upload a small sample project with this issue. We could examine it and figure out what should be changed to make it work.

12

Yes, I think it will be simpler.

Here is the project https://github.com/sebsheep/decision_tree

I don’t know how yet to specify what package install with opam (like the “requirements.txt” in python or “package.json” with npm). The dependencies are: ounit2 and angstrom.

thank you for your time!

13

That’s in a .mli file. To include the contents of another module, the corresponding signature item is include module type of Types. To expand a bit on this:

  • Types is a module.
  • its (inferred) module type is module type of Types
  • in mli files, include expects a module type (which does not necessarily correspond to a module in particular, which is why you can do include Set.OrderedType)
1 Like
14

Ah it’s in the mli didn’t catch that indeed !

1 Like
15

Additionally, you can change

(library 
    (name BooleanFormulae)
    (libraries angstrom)
    (preprocess (pps ppx_deriving.show ppx_deriving.ord)))

to

(library 
    (name BooleanFormulae)
    (libraries angstrom)
    (modules parser types)
    (preprocess (pps ppx_deriving.show ppx_deriving.ord)))

to be able to access BooleanFormulae.Parser from main.ml.

1 Like