Re: [Caml-list] Float precision in OCaml

[Peter Thiemann <thiemann@informatik.uni-freiburg.de>]

Hi Michael,

> On 1. Aug 2017, at 19:12, Soegtrop, Michael <michael.soegtrop@intel.com> wrote:
> 
> Dear Peter,
> 
>> https://cseweb.ucsd.edu/~lerner/papers/fp-printing-popl16.pdf
> 
> A very interesting paper, but it handles only the print direction, not the scan direction and not the problem of:
> 
> forall (x : double): scan(print(x)) = x

That’s true. A bit further digging produces this report:
https://arxiv.org/abs/1310.8121
Which claims such round-tripping with a fairly simple algorithm. 
Disclaimer: I only skimmed this paper.

-Peter

> 
> Best regards,
> 
> Michael
> 
>> -----Original Message-----
>> From: Peter Thiemann [mailto:thiemann@informatik.uni-freiburg.de]
>> Sent: Tuesday, August 1, 2017 5:49 PM
>> To: Soegtrop, Michael <michael.soegtrop@intel.com>
>> Cc: Peter Thiemann <thiemann@informatik.uni-freiburg.de>; Daniel Bünzli
>> <daniel.buenzli@erratique.ch>; Viet Le <vietlq85@gmail.com>; caml-
>> list@inria.fr
>> Subject: Re: [Caml-list] Float precision in OCaml
>> 
>> BTW, there is some literature on this topic, the most recent of which is the
>> paper “Printing Floating Point Numbers - A faster, always correct method”
>> https://cseweb.ucsd.edu/~lerner/papers/fp-printing-popl16.pdf
>> 
>> It cites all the previous efforts starting with Knuth’s TACP Vol II, seminumerical
>> algorithms.
>> 
>> -Peter
>> 
>>> On 1. Aug 2017, at 15:57, Soegtrop, Michael <michael.soegtrop@intel.com>
>> wrote:
>>> 
>>> Said that, one can define a mapping from floating point numbers to usual
>> decimal string representations and back such that each floating point number
>> results in a unique string. It is just quite tricky to get it right without extended
>> precision arithmetic, though.
>>> 
>>> As far as I know the Lisp standard requires that certain floating point formats
>> have this property (I need to check). One might be able to learn from them how
>> to do this properly.
> 
> Intel Deutschland GmbH
> Registered Address: Am Campeon 10-12, 85579 Neubiberg, Germany
> Tel: +49 89 99 8853-0, www.intel.de
> Managing Directors: Christin Eisenschmid, Christian Lamprechter
> Chairperson of the Supervisory Board: Nicole Lau
> Registered Office: Munich
> Commercial Register: Amtsgericht Muenchen HRB 186928