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From: Xavier Leroy <xavier.leroy@inria.fr>
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Date: Thu, 26 May 2016 10:57:41 +0200
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Subject: Re: [Caml-list] Is this a bug in Num.float_of_num ?

On 26/05/2016 10:24, Mohamed Iguernlala wrote:
> Hi,
> 
> I came to the following "stange" behavior when using the function
> float_of_num. I don't know if this should be considered as a bug,
> since this function has no specification (in num.mli *)
> 
> The float "f = 6004799503160661. /. 18014398509481984." has an
> exact representation on 64 bits. Its value is
> 
> 0.333333333333333314829616256247390992939472198486328125
> 
> However, when using float_of_num to compute the float corresponding to
> the number above represented as a num, the result is slightly different.

float_of_ratio and float_of_num are very imprecise in OCaml 4.02 and
earlier.  They were reimplemented in OCaml 4.03 in a way that should
give correct roundings.  So, make sure you're using 4.03, and if the
bug is still there, please file a report on Mantis.

Best,

- Xavier Leroy