Re: float_to_list(X)

~p is a lossless format for floats that uses a conservative number of
digits (since R12B02). See OTP-7084. The implementation was based on
mochinum:digits/1 from mochiweb.

On Fri, May 7, 2021 at 03:26 Richard O'Keefe <[email protected]> wrote:

> No, making float_to_list/1 a wrapper for format... does not make sense.
> float_to_list/1 is meant to give you an accurate representation of the
> value.  Two different floats, no matter how small the difference,
> should result in different lists.  It's meant for converting a float
> to text that you can send to another machine and reconstitute the
> same value there.  This will usually result in more digits than a human
> would normally want to see.
>
> If you *want* format ~p, use it!
>
> Now perhaps there might be an argument to be made for
> float_to_list(X: number(), N: integer()) -> string()
> returning a string that represents X as accurately as
> possible using N digits.  But that is another discussion.
>
> On Thu, 6 May 2021 at 20:56, Themba Jonga <[email protected]> wrote:
>
>> Hi, again.
>>
>> Following a response I got from Dmitry Klionsky, perhaps it makes sense
>> for *float_to_list(N)* to be made into a wrapper for
>> *lists:flatten(io_lib:format("~p",[N]))?*
>>
>> Eshell V11.1  (abort with ^G)
>> 1> N = 4.4445.
>> 4.4445
>> 2> lists:flatten(io_lib:format("~p",[N])).
>> "4.4445"
>> 3> P = 5.4443.
>> 5.4443
>> 4> lists:flatten(io_lib:format("~p",[P])).
>> "5.4443"
>> 5> Q = 1.2345678.
>> 1.2345678
>> 6> lists:flatten(io_lib:format("~p",[Q])).
>> "1.2345678"
>> 7> float_to_list(Q).
>> "1.23456779999999999298e+00"
>> 8>
>>
>> Regards
>>
>> *Themba Jonga*
>>
>>
>>
>>
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>>
>> On Wed, 5 May 2021 at 18:38, Scott Ribe <[email protected]>
>> wrote:
>>
>>> > On May 5, 2021, at 10:20 AM, [email protected] wrote:
>>> >
>>> > In short, no.
>>>
>>> Although many (most, actually nearly all) real numbers cannot be
>>> represented precisely as a float, any float can be round-tripped to text
>>> and back exactly. This is part of the IEEE floating point standard,
>>> actually. (And it's not easy...)
>>>
>>>
>>>
>>
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>>
>