Compile a first program

1) Create a file sum.ml

2) Write this code

open Base
open Stdio

let rec read_and_accumulate accum =
  let line = In_channel.input_line In_channel.stdin in
  match line with
  | None -> accum
  | Some x -> read_and_accumulate (accum +. Float.of_string x)

let () =
  printf "Total: %F\n" (read_and_accumulate 0.)

3) create dune file

(executable
 (name      sum)
 (libraries base stdio))

4) install Stdio

opam install Stdio 

5) Use dune to build the binary

dune build sum.ml

6) Execute the program type some number and hit CTRL+d

./_build/default/sum.exe