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From: "=?utf-8?b?TWF0dGlhcyBFbmdkZWfDpQ==?=  =?utf-8?b?cmQ=?=" <mattias@virtutech.se>
To: olivier.roussel@crans.org
Cc: yinso.chen@gmail.com, caml-list@yquem.inria.fr
In-reply-to: <47016CEE.8010704@crans.org> (message from Olivier Roussel on
	Mon, 01 Oct 2007 23:55:58 +0200)
Subject: Re: [Caml-list] best and fastest way to read lines from a file?
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References: <779bf2730710011427g5983da4cw6ad8b715a9e38771@mail.gmail.com> <47016CEE.8010704@crans.org>
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X-Spam: no; 0.00; mattias:01 mattias:01 readline:01 rec:01 rec:01 avoids:01 exception:01 caml-list:01 int:01 match:02 let:03 let:03 raise:03 file:11 file:11 

>let line_count filename =
>   let f = open_in filename in
>   let rec loop count =
>     match (readline f) with
>       | Some(_) -> loop (count+1)
>       | None -> count in
>   loop 0;;

Something like this should be even faster:

exception Done of int

let line_count file =
  let rec loop count =
    let _ =
      try
	input_line f
      with End_of_file -> raise (Done count)
    in
      loop (count + 1)
  in
    try loop 0 with Done x -> x

as it avoids unnecessary consing in the inner loop.