A Commonplace BookOCaml Learning-II
Project Creation and Package Management
Why
This brief note serves to record project management tools and precedures for
creating OCaml projects.
How
Package Management
The most important aspect of open-source development is for your code to be
published and utilized by other users. In order to do that, it is essential to
have a replicable environment and clean project structure. The
PkgTemplates.jl is a Julia package for creating new Julia packages. It has
spoiled me for being easy to use, having clean project generation, having
no extra dependency on other tools, and has good synergy with github. In
OCaml ecosystem, there are few options like PkgTemplates.jl such as spin
and pesy. However, drom, a wrapper over opam and dune, resembles
PkgTemplates.jl the most. Therefore, I will adopt to use it. It should be
noted however the other two tools has their own strengths. For example, spin
has more templates than drom. Underthe hood, drom uses opam for
environment management and dune for project management and project building.
Drom Installation
drom is a OCaml package. Therefore, it can be installed using opam. To do
so, use the following command:
opam install dromDrom Usage
In order to create a project skeleton, we could use the following code
drom new PKG-NAME --skeleton SKELETON-NAMEThere are six possible SKELETON-NAME:
virtuallibraryprogrammini-libmini-prgppx_deriver
The details of each skeleton is beyond the scope of this note. Interested reader
will find their documentation helpful. We will continue this note with program
skeleton. Within the program project structure, there are two sub-structure in
the src folder. They are known as the driver, it has the same name as the
library, and the library, it has the name appended with the _lib postfix.
The driver contains all executable functions of the project. It may call
functions in the library or outer libraries. The library serves as a place
for providing helper or general features that can potentially be used in other
libraries and the current project but is not implement anywhere else. As of
writing this note, it is not clear how to add other library to an existing
package. A possible way will be to manually add [package] section to the main
project drom.toml file.
Customization
There are a few things we would like to change based on the skeleton. We could
do that by first editing the drom.toml file and them run drom project to
update the project structure. More specifically, we could also change the
configuration for the package content or the package library content.
Menhir
For more details, please refer to drom documentation.
Build Project
You may build the project with drom build -y and then run it with drom run.
There are other convinent options like building the documentation and installing
the written package into a global opam environment. You may find details in
drom's documentation helpful.
How to manage environment in OCaml
No language is of any use without good libraries. The libraries in OCaml are
managed by a tool called opam. The environments in OCamel are termed as
switches. To create a new switch, use the following command:
opam switch create <switch-name> <compiler-version>For example, to create a switch named ocaml-4.10.0, use the following
command:
opam switch create ocaml-4.10.0 ocaml-base-compiler.4.10.0To list all the switches, use the following command:
opam switch listTo switch to a different switch, use the following command:
opam switch set <switch-name>Resources
How to create a Project in OCaml
The tool that is needed to create a project in OCaml is called dune. To create
a new project, you could do
dune init proj helloModules in OCaml
Modules in OCaml are similar to namespaces in C++. They are used to organize
functions and types. Each module is defined in a file with the same name as the
module. For example, the module List is defined in the file List.ml. The
lib/ModuleName.ml is the file that defines the module Module. The
lib/ModuleName.mli is the file where you decide which functions and types to
make public.
Install Modules
opam isntall packageName