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From: Thorsten Ohl <ohl@hep.tu-darmstadt.de>
To: Caml List <caml-list@pauillac.inria.fr>
Cc: Xavier Leroy <xavier.leroy@inria.fr>
Date: Fri, 9 Nov 2001 14:32:18 +0100	[thread overview]
Message-ID: <15339.56034.169961.457637@heplix4.ikp.physik.tu-darmstadt.de> (raw)
In-Reply-To: <20011109131841.A5769@pauillac.inria.fr>

> Starting with OCaml 3.01, the Int64 module provides two functions
> "bits_of_float" and "float_of_bits" which convert between floats and
> an int64 matching the underlying 64-bit representation of the float.

Thanks.  I forgot to look among the Int* modules when I was hunting
for floating point conversions :-(.

> >     external float_of_bytes : string -> float = "float_of_bytes"
> >    b) on little endian machines one has to swap bytes.
>
> b) is not (big endian representation is enforced).

Now I'm confused.  On my Linux box, I have to swap bytes in order
to read binary floating point numbers from a stream (where I can not
mmap Bigarrays).

    let unsafe_rev8 s =
      let swap i1 i2 =
        let tmp = String.unsafe_get s i1 in
        String.unsafe_set s i1 (String.unsafe_get s i2);
        String.unsafe_set s i2 tmp in
      swap 0 7;
      swap 1 6;
      swap 2 5;
      swap 3 4

    let little_endian = true

    let input_binary_float ic =
      let buf = String.create 8 in
      really_input ic buf 0 8;
      if little_endian then
        unsafe_rev8 buf;
      float_of_bytes buf

But that's academical, because I will switch to Int64 now.  Thanks
again.
-- 
Thorsten Ohl, Physics Department, TU Darmstadt -- ohl@hep.tu-darmstadt.de
http://heplix.ikp.physik.tu-darmstadt.de/~ohl/ [<=== PGP public key here]
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  reply	other threads:[~2001-11-09 13:32 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-11-09  3:29 [Caml-list] how to split up a Caml float into its component bytes Rafael 'Dido' Sevilla
2001-11-09 11:05 ` Thorsten Ohl
2001-11-09 12:18   ` Xavier Leroy
2001-11-09 13:32     ` Thorsten Ohl [this message]
2001-11-09 11:28 ` malc
2001-11-09 17:09 ` Ken Rose

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