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How to use Stream.iter to process stdin strings in OCaml

I am trying to process data from stdin in a linearly oriented fashion in OCaml, but I am having problems getting types to align with Stream.iter. I found the following code snippet on the OCaml website ( http://ocaml.org/learn/tutorials/streams.html ):

let line_stream_of_channel channel =
    Stream.from
      (fun _ ->
         try Some (input_line channel) with End_of_file -> None)

Using this, I wrote a simple function that reads a line, does a few things, and prints some data back. I will return to the details, as I believe that the function works fine. It must be of type string -> unit, although, like (for example) print_endline, the error that I get from the compiler is the same whether I pass my function to or print_endlineto Stream.iter.

Here's the call:

let read_data =
  Stream.iter ~f:print_summary (line_stream_of_channel In_channel.stdin)

The error received from the compiler is this:

Error: The function applied to this argument has type 'a Stream.t -> unit
This argument cannot be applied with label ~f

Stream.iter . , , print_endline 'a Stream.t -> unit - string -> unit, ?

+3
1

'a Stream.t -> unit Stream.iter. , Stream.iter . f, .

~f:. ( , .)

+3

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