Basic Ocaml: How do I compile this? - ocaml

Question

Just beginning with ocaml and am struggling with the various compilers and tooling. E.g. ocamlopt, ocamlc, ocamlbuild, corebuild and so on. So, how do I compile the following?
open Core.Std
module Regex = Re2.Regex
let ls pattern =
let pat = Regex.create_exn pattern in
let matcher = Regex.matches pat in
Sys.ls_dir "."
|> List.filter ~f:matcher
|> List.iter ~f:(fun s -> print_string s; print_newline ())
let () =
match In_channel.input_line stdin with
| None -> print_string "No Input"
| Some pat -> ls pat
In utop I can just #require "re2" and go from there.
Without the inclusion of the regular expressions module I would just use corebuild ls.native, assuming that the above code is placed into ls.ml.
[edit]
Have so far tried
ocamlbuild -use-ocamlfind -package core -package re2
which spit out
ocamlfind ocamldep -package core -package re2 -modules ls.ml > ls.ml.depends
ocamlfind ocamlc -c -package core -package re2 -o ls.cmo ls.ml
+ ocamlfind ocamlc -c -package core -package re2 -o ls.cmo ls.ml
ocamlfind: Error from package `threads': Missing -thread or -vmthread switch
Command exited with code 2.
So after some googling I was led to this blog I tried
ocamlbuild -tag thread -use-ocamlfind -package core -package re2
which spits out over 6000 lines of what looks like make output before failing with:
collect2: error: ld returned 1 exit status
File "caml_startup", line 1:
Error: Error during linking
Command exited with code 2.
so I'm not sure what to try next.

Answer 1

I am using Ubuntu 14.04 on a 64bit machine. I ditched the apt-get versions of ocaml:
sudo apt-get remove --purge ocaml ocaml-base-nox ocaml-compiler-libs \
ocaml-interp ocaml-native-compilers \
ocaml-nox campl4 ocaml-base ocaml-docs opam
Then I installed opam from source according to the instructions here.
Next I installed core, utop, and re2 with opam install core utop re2
And finally I ran ocamlbuild -use-ocamlfind -package re2 -package core -tag thread ls.native
which built the desired executable.

Answer 2

I would suggest you to use oasis tool. It is not as hard, as one may think. But it removes all library burden from you.
Lets create a simple _oasis file for your project:
OASISFormat: 0.4
Name: ls
Version: 0.1
Synopsis: Testing oasis
Authors: Fizz_ed
License: MIT
Plugins: META (0.4), DevFiles (0.4)
BuildTools: ocamlbuild, camlp4o
BuildDepends: core, camlp4, threads,
sexplib.syntax,
bin_prot.syntax,
comparelib.syntax,
herelib,
herelib.syntax
Executable "ls"
Path: .
MainIs: ls.ml
CompiledObject: best
BuildDepends: re2
After you've created this file, run oasis setup command (if oasis is not installed, then install it using opam, or your package manager).
After that you will have a common configure script and makefiles. So all you need is to type
./configure
make
and your file will be compiled.
Or you can just use ocamlbuild directly, it will work too, since oasis created all the necessary files
ocamlbuild ls.native
A few explanations about the file. The preamle contains everything you need to build your core-style applications.
Executable section describes your executable file, and also adds a dependency to re2 library.
Update: fixed some issues.