# Structure the code in modules **URL:** \ **Category:** Learning\ **Tags:** module, dune\ **Created:** [March 29, 2020, 2:42pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401 "2020-03-29T14:42:29Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![sebbes](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/sebbes/32/1997_2.png) [@sebbes](https://discuss.ocaml.org/u/sebbes)\ **Post date:** [March 29, 2020, 2:42pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/1 "2020-03-29T14:42:30Z")
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](https://stackoverflow.com/a/53325230/3421913) ) : ```auto ├── 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: ```auto (executable (name main) (libraries BooleanFormulae)) ``` Here is `lib/dune`: ```auto (library (name BooleanFormulae) (libraries angstrom) (preprocess (pps ppx_deriving.show ppx_deriving.ord))) ``` In the dune docs ([Stanza Reference — Dune documentation](https://dune.readthedocs.io/en/stable/dune-files.html)), 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: ```auto 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? ---
**Author:** ![sebbes](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/sebbes/32/1997_2.png) [@sebbes](https://discuss.ocaml.org/u/sebbes)\ **Post date:** [March 29, 2020, 2:51pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/2 "2020-03-29T14:51:25Z")
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`: ```auto (test (name test) (libraries BooleanFormulae ounit2)) ``` ---
**Author:** ![giltho](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/giltho/32/3521_2.png) [@giltho](https://discuss.ocaml.org/u/giltho)\ **Post date:** [March 29, 2020, 2:59pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/3 "2020-03-29T14:59:05Z")
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 ---
**Author:** ![sebbes](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/sebbes/32/1997_2.png) [@sebbes](https://discuss.ocaml.org/u/sebbes)\ **Post date:** [March 29, 2020, 3:04pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/4 "2020-03-29T15:04:30Z")
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: ```auto 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 ``` ---
**Author:** ![giltho](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/giltho/32/3521_2.png) [@giltho](https://discuss.ocaml.org/u/giltho)\ **Post date:** [March 29, 2020, 3:40pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/5 "2020-03-29T15:40:23Z")
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: ```auto module Parser = Parser ``` and in your booleanFormulae.mli you need ```auto module Parser : sig ... end ``` ---
**Author:** ![sebbes](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/sebbes/32/1997_2.png) [@sebbes](https://discuss.ocaml.org/u/sebbes)\ **Post date:** [March 29, 2020, 7:12pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/6 "2020-03-29T19:12:43Z")
Thank you, problem solved for the `BooleanFormulae.Parser`. I still have an issue with the tests: ```auto $ 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`) ---
**Author:** ![yawaramin](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/yawaramin/32/3384_2.png) [@yawaramin](https://discuss.ocaml.org/u/yawaramin)\ **Post date:** [March 30, 2020, 2:11am UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/7 "2020-03-30T02:11:30Z")
Does it work if you prefix the constructor with its module name: `BooleanFormulae.Types.Var`? ---
**Author:** ![giltho](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/giltho/32/3521_2.png) [@giltho](https://discuss.ocaml.org/u/giltho)\ **Post date:** [March 30, 2020, 11:44am UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/8 "2020-03-30T11:44:49Z")
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 ? ---
**Author:** ![sebbes](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/sebbes/32/1997_2.png) [@sebbes](https://discuss.ocaml.org/u/sebbes)\ **Post date:** [March 30, 2020, 1:00pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/9 "2020-03-30T13:00:11Z")
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”: ```auto File "BooleanFormulae/booleanFormulae.mli", line 2, characters 8-13: 2 | include Types ^^^^^ Error: Unbound module type Types ``` ---
**Author:** ![giltho](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/giltho/32/3521_2.png) [@giltho](https://discuss.ocaml.org/u/giltho)\ **Post date:** [March 30, 2020, 2:30pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/10 "2020-03-30T14:30:34Z")
`include Types` doesn’t work but `open Types` does ? that doesn’t sound right ---
**Author:** ![yawaramin](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/yawaramin/32/3384_2.png) [@yawaramin](https://discuss.ocaml.org/u/yawaramin)\ **Post date:** [March 30, 2020, 3:11pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/11 "2020-03-30T15:11:47Z")
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. ---
**Author:** ![sebbes](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/sebbes/32/1997_2.png) [@sebbes](https://discuss.ocaml.org/u/sebbes)\ **Post date:** [March 30, 2020, 3:31pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/12 "2020-03-30T15:31:44Z")
Yes, I think it will be simpler. Here is the project [https://github.com/sebsheep/decision\_tree](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! ---
**Author:** ![emillon](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/emillon/32/1206_2.png) [@emillon](https://discuss.ocaml.org/u/emillon)\ **Post date:** [March 31, 2020, 8:10am UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/13 "2020-03-31T08:10:39Z")
> [@giltho](#): > > `include Types` doesn’t work but `open Types` does ? that doesn’t sound right 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`) ---
**Author:** ![giltho](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/giltho/32/3521_2.png) [@giltho](https://discuss.ocaml.org/u/giltho)\ **Post date:** [March 31, 2020, 9:47am UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/14 "2020-03-31T09:47:03Z")
Ah it’s in the mli didn’t catch that indeed ! ---
**Author:** ![chrisnevers](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/chrisnevers/32/1854_2.png) [@chrisnevers](https://discuss.ocaml.org/u/chrisnevers)\ **Post date:** [April 10, 2020, 7:07pm UTC](https://discuss.ocaml.org/t/structure-the-code-in-modules/5401/15 "2020-04-10T19:07:41Z")
Additionally, you can change ```auto (library (name BooleanFormulae) (libraries angstrom) (preprocess (pps ppx_deriving.show ppx_deriving.ord))) ``` to ```auto (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`.