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Message-ID: <47016CEE.8010704@crans.org>
Date: Mon, 01 Oct 2007 23:55:58 +0200
From: Olivier Roussel <olivier.roussel@crans.org>
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To: YC <yinso.chen@gmail.com>
Cc: caml-list@yquem.inria.fr
Subject: Re: [Caml-list] best and fastest way to read lines from a file?
References: <779bf2730710011427g5983da4cw6ad8b715a9e38771@mail.gmail.com>
In-Reply-To: <779bf2730710011427g5983da4cw6ad8b715a9e38771@mail.gmail.com>
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X-Spam: no; 0.00; ocaml:01 printf:01 printf:01 recursive:01 readline:01 readline:01 crans:98 2.5:98 rec:01 rec:01 caml-list:01 exceptions:01 match:02 python:03 let:03 

YC a écrit :
> Hi all -
Hi!
> OCaml code:
> (* test.ml <http://test.ml> *)
> let rec line_count filename =
>   let f = open_in filename in
>   let rec loop file count =
>     try
>       ignore (input_line file);
>       loop file (count + 1)
>     with
>       End_of_file -> count
>   in
>     loop f 0;;
> 
> let count = line_count <345k-line.txt> in
>     Printf.printf "Done: %d" count;;
The following solution is ~2.5x faster than the Python implementation on 
my computer. Because there is no more exceptions in recursive calls, and 
thanks to tail-recursion.

let readline f =
   try Some (input_line f)
   with End_of_file -> None;;

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;;

let count = line_count <345k-line.txt> in
Printf.printf "Done: %d\n" count;;


-- 
Olivier Roussel