demonstrator of oi with Base/ppx

foo.ml

[@@@opam base stdio ppx_jane]

open Base
open Stdio

type t = { bar: float } [@@deriving sexp]

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 () =
  let t = { bar=read_and_accumulate 0. } in
  printf "Total: %s\n" (Sexp.to_string_hum (sexp_of_t t))