[erlang-patches] new float_to_list/2

Björn-Egil Dahlberg egil@REDACTED
Fri Jan 18 15:59:16 CET 2013 

In review .. again =)

I think we have covered default behaviours.

Is the following intended behaviour? =)

1> erlang:float_to_list(3/7, [{decimals, 314}, compact]).
[48,46,52,50,56,53,55,49,52,50,56,53,55,49,52,50,56,53,52,
  55,54,51,56,48,55,56,48,52,51|...]

2> erlang:float_to_list(3/7, [{scientific, 314}, compact]).
"4.2857142857142854763807804374664556235074996948242187500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"

?

// Björn-Egil

On 2013-01-14 10:10, Fredrik wrote:
> Hello,
> This testcase is failing:
> Suite: bif_SUITE
> Testcase: specs
> Reason:
> The following BIFs don't have specs:
>
> erlang:float_to_list/2
> Give me notice when this is done,
> BR Fredrik Gustafsson
> Erlang OTP Team
> On 01/11/2013 04:55 PM, Serge Aleynikov wrote:
>> Sorry the test case line was the "last moment" add on.  It is fixed now
>> in my branch below.
>>
>> On 1/11/2013 10:44 AM, Fredrik wrote:
>>> Hey,
>>> Your patch does not build:
>>> "
>>>
>>> emulator_test ../emulator_test/num_bif_SUITE.erl:130: illegal pattern
>>> "
>>>
>>>
>>> Please have a look at it, and give me notice when you are done.
>>>
>>> BR Fredrik Gustafsson
>>> Erlang OTP Team
>>> On 01/11/2013 03:11 PM, Serge Aleynikov wrote:
>>>> Ok. Here's the patch rebased to master:
>>>>
>>>> git fetchhttps://github.com/saleyn/otp/tree/float_to_list_2
>>>>
>>>> https://github.com/saleyn/otp/compare/master...float_to_list_2
>>>> https://github.com/saleyn/otp/compare/master...float_to_list_2.patch
>>>>
>>>> Regards,
>>>>
>>>> Serge
>>>>
>>>> On 1/11/2013 8:53 AM, Björn-Egil Dahlberg wrote:
>>>>> On 2013-01-11 14:24, Serge Aleynikov wrote:
>>>>>> While looking at this I see that the code in folder
>>>>>> "erts/emulator/sys/vxworks" is present in maint but missing in the
>>>>>> master branch.  Is this intentional?  If so, should I remove the
>>>>>> part of
>>>>>> the patch designed for vxworks?
>>>>> Yes. Any and all vxworks support has been removed in R16 from OTP except
>>>>> for epmd, erl_interface and ic.
>>>>>
>>>>> // Björn-Egil
>>>>>> On 1/11/2013 3:52 AM, Fredrik wrote:
>>>>>>> Hey,
>>>>>>> Could you please rebase this on current 'master' branch?
>>>>>>>
>>>>>>> BR Fredrik Gustafsson
>>>>>>> Erlang OTP Team
>>>>>>> On 01/11/2013 04:06 AM, Serge Aleynikov wrote:
>>>>>>>> I implemented Lukas's recommendations that were presenting an
>>>>>>>> acceptance
>>>>>>>> issue of the new function, so the current version of the patch does:
>>>>>>>>
>>>>>>>> 1. float_to_list/1 is backwards compatible.
>>>>>>>> 2. float_to_list(X,[]) gives the same result as float_to_list(X).
>>>>>>>> 3. float_to_list(X,[{decimals,N}]) uses the new fast implementation
>>>>>>>> (with the optional compact option).
>>>>>>>> 4. float_to_list(X,[{scientific,M}]) gives the same result as
>>>>>>>> float_to_list(X) with the ability to control the number of decimals.
>>>>>>>>
>>>>>>>> The only item from Lucas's list that I left unchanged was the
>>>>>>>> modification to erts/lib_src/common/erl_printf_format.c to take
>>>>>>>> advantage of the speed improvement of the new implementation.  I am
>>>>>>>> including a patch in this email that implements this logic, but I
>>>>>>>> decided to leave the integration task to the OTP team since
>>>>>>>> erl_printf_format.c is actually compiled into a liberts_internal.a
>>>>>>>> library and I didn't want to introduce a dependency of it on other
>>>>>>>> code
>>>>>>>> - this should be decided by maintainers.
>>>>>>>>
>>>>>>>> The test cases of float_to_list/{1,2} have been updated.
>>>>>>>>
>>>>>>>> git fetchhttps://github.com/saleyn/otp/tree/float_to_list_2
>>>>>>>>
>>>>>>>> https://github.com/saleyn/otp/compare/maint...float_to_list_2
>>>>>>>> https://github.com/saleyn/otp/compare/maint...float_to_list_2.patch
>>>>>>>>
>>>>>>>> Regards,
>>>>>>>>
>>>>>>>> Serge
>>>>>>>>
>>>>>>>> On 8/23/2012 5:10 AM, Lukas Larsson wrote:
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> I'll put it in the backlog and we'll see if it gets prioritized for
>>>>>>>>> R16B.
>>>>>>>>>
>>>>>>>>> As always if you (or someone else) wants make sure it gets in, the
>>>>>>>>> best
>>>>>>>>> way to ensure that is to send an updated patch.
>>>>>>>>>
>>>>>>>>> Lukas
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 22/08/12 21:17, Serge Aleynikov wrote:
>>>>>>>>>> I am certainly very happy to hear that you finally agreed to
>>>>>>>>>> include
>>>>>>>>>> this in the distribution.  The changes proposed below seem
>>>>>>>>>> reasonable
>>>>>>>>>> and simple.  Will the OTP team be able to modify my patch to
>>>>>>>>>> implement
>>>>>>>>>> them?
>>>>>>>>>>
>>>>>>>>>> On 8/22/2012 12:01 PM, Lukas Larsson wrote:
>>>>>>>>>>> Hello Serge!
>>>>>>>>>>>
>>>>>>>>>>> I think we have finally agreed how we want this functionality to
>>>>>>>>>>> work.
>>>>>>>>>>>
>>>>>>>>>>> float_to_list/1 should be left as it is now for backwards
>>>>>>>>>>> compatibility.
>>>>>>>>>>> float_to_list(1.0,[]) should give the same as float_to_list(1.0).
>>>>>>>>>>> float_to_list(1.0,[{decimals,X}]) should use your faster
>>>>>>>>>>> implementation
>>>>>>>>>>> (with the optional compact option).
>>>>>>>>>>> float_to_list(1.0,[{scientific,Y}]) should give the same as
>>>>>>>>>>> float_to_list(1.0) if Y is 20.
>>>>>>>>>>>
>>>>>>>>>>> We would also like the string rendering part of
>>>>>>>>>>> sys_double_to_chars_fast
>>>>>>>>>>> to be put into
>>>>>>>>>>> erts/lib_src/common/erl_printf_format.c:fmt_double. This
>>>>>>>>>>> way other parts of the vm which print floats will benefit from
>>>>>>>>>>> your
>>>>>>>>>>> changes!
>>>>>>>>>>>
>>>>>>>>>>> I hope our indecisiveness have not caused you to shy away from
>>>>>>>>>>> taking
>>>>>>>>>>> this feature into Erlang/OTP. If you have any further questions or
>>>>>>>>>>> ponderings just let me know.
>>>>>>>>>>>
>>>>>>>>>>> Lukas
>>>>>>>>>>>
>>>>>>>>>>> On 18/07/12 20:47, Serge Aleynikov wrote:
>>>>>>>>>>>> On 7/18/2012 5:18 AM, Lukas Larsson wrote:
>>>>>>>>>>>>> However, I would also like the fast functionality to be used by
>>>>>>>>>>>>> float_to_list_1 as well, is possible to do this and stay
>>>>>>>>>>>>> backwards
>>>>>>>>>>>>> compatible? Hopefully you just have to shift the comma and add
>>>>>>>>>>>>> e+XX at
>>>>>>>>>>>>> the end of the optimized case and call sys_double_to_chars
>>>>>>>>>>>>> for the
>>>>>>>>>>>>> unoptimized.
>>>>>>>>>>>> See my comments below regarding 'scientific' option.  Since
>>>>>>>>>>>> float_to_list_2 is a new function I would think that you are
>>>>>>>>>>>> questioning
>>>>>>>>>>>> the issue of backward compatibility only in terms of converting
>>>>>>>>>>>> float_to_list_1 to use float_to_list_2 implementation.
>>>>>>>>>>>> However, I
>>>>>>>>>>>> think
>>>>>>>>>>>> that this will have adverse performance tax on float_to_list_2,
>>>>>>>>>>>> which
>>>>>>>>>>>> will diminish the benefit.  It's been a while however, since I
>>>>>>>>>>>> wrote
>>>>>>>>>>>> that patch, perhaps there's a way to retrofit scientific notation
>>>>>>>>>>>> without a performance penalty.
>>>>>>>>>>>>
>>>>>>>>>>>> It's more than simple shifting of the comma, since there's also
>>>>>>>>>>>> rounding
>>>>>>>>>>>> involved.
>>>>>>>>>>>>
>>>>>>>>>>>> This case is easy:
>>>>>>>>>>>>
>>>>>>>>>>>> 4>  float_to_list(1.01234).
>>>>>>>>>>>> "1.01234000000000001762e+00"
>>>>>>>>>>>> 5>  float_to_list(1.01234, [{decimals, 20}]).
>>>>>>>>>>>> "1.01234000000000001762"
>>>>>>>>>>>>
>>>>>>>>>>>> This case is a bit more complex (illustration of rounding
>>>>>>>>>>>> impact):
>>>>>>>>>>>>
>>>>>>>>>>>> 7>  float_to_list(10123412345.0123451234).
>>>>>>>>>>>> "1.01234123450123443604e+10"
>>>>>>>>>>>> 8>  float_to_list(10123412345.0123451234, [{decimals, 20}]).
>>>>>>>>>>>> "10123412345.01234436035156250000"
>>>>>>>>>>>>
>>>>>>>>>>>>> Also float_to_list(1.0) should return the same thing as
>>>>>>>>>>>>> float_to_list(1.0,[]), otherwise the API will be inconsistent
>>>>>>>>>>>>> with how
>>>>>>>>>>>>> other such APIs work.
>>>>>>>>>>>> Actually if you trace this subject back there was another
>>>>>>>>>>>> request that
>>>>>>>>>>>> the default number of decimals is chosen to be consistent with
>>>>>>>>>>>> what
>>>>>>>>>>>> printf() does, so I changed the implementation to accommodate
>>>>>>>>>>>> that
>>>>>>>>>>>> request:
>>>>>>>>>>>>
>>>>>>>>>>>> Eshell V5.9  (abort with ^G)
>>>>>>>>>>>> 1>  float_to_list(1.0, []).
>>>>>>>>>>>> "1.000000"
>>>>>>>>>>>>
>>>>>>>>>>>> Which is different from the default of float_to_list/1:
>>>>>>>>>>>>
>>>>>>>>>>>> 2>  float_to_list(1.0).
>>>>>>>>>>>> "1.00000000000000000000e+00"
>>>>>>>>>>>>
>>>>>>>>>>>> Maybe one could introduce a 'scientific' option to
>>>>>>>>>>>> float_to_list/2, to
>>>>>>>>>>>> use the float_to_list/1 implementation?
>>>>>>>>>>>>
>>>>>>>>>>>> Serge
>>>>>>>>>>>>
>>>>>>>>>>>>> On 24/05/12 16:02, Serge Aleynikov wrote:
>>>>>>>>>>>>>> Henrik,
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Fetch:    git fetch
>>>>>>>>>>>>>> https://github.com/saleyn/otp/tree/float_to_list_2
>>>>>>>>>>>>>> Diff:https://github.com/saleyn/otp/compare/float_to_list_2
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I added the definition for the new BIF to make the type checker
>>>>>>>>>>>>>> happy:
>>>>>>>>>>>>>> https://github.com/saleyn/otp/commit/f9ddbeda5426ca83cda03c06a9860220ea4a22c7
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Once you do the "otp_build tests", how do you execute all tests
>>>>>>>>>>>>>> suites
>>>>>>>>>>>>>> in $ERL_TOP or if possible only tests in a given SUITE?  I
>>>>>>>>>>>>>> tried the
>>>>>>>>>>>>>> following but all tests fail:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> [otp/erts/emulator/test]$ ../../../bin/erl -noshell -s
>>>>>>>>>>>>>> test_server_ctrl
>>>>>>>>>>>>>> run_test DIR "." -s erlang halt
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> I did however run individual tests in bif_SUIT:types to make
>>>>>>>>>>>>>> sure my
>>>>>>>>>>>>>> patch didn't break anything.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Serge
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On 5/24/2012 5:17 AM, Henrik Nord wrote:
>>>>>>>>>>>>>>> Hi again.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> This test is not passing: emulator/bif_SUIT:types
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> No type information:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> [{erlang,float_to_list,2}]
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On 04/21/2012 07:19 AM, Serge Aleynikov wrote:
>>>>>>>>>>>>>>>> git fetchhttps://github.com/saleyn/otp/tree/float_to_list_2
>>>>>>>>>>>>>> _______________________________________________
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>>>>>>>>>>>>>>
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