[Scilab-users] Bitget for int64/uint64

[Jan Åge Langeland]

Samuel

My suggestion for a workaround (looks like my first reply disappeared):

b  =uint64(2)^61+1

bb2=uint64(bin2dec(strsplit(strrev(bitstring(b))))');

bb1=bitget(b,1:64);

bb2(1)-bb1(1)

  ans  =  1

A bit of a waste to use uint64 to store single bits, but that is what 
bitget does:

--> typeof(bb1)
  ans  =  "uint64"

Jan


On 2020-02-27 17:51 PM, Samuel Gougeon wrote:
> As suspected, the bug originates from the * operator, that is still 
> not reliable between uint64 or int64:
> --> b
>  b  =
>   230584300921369395*5*
>
> --> b * uint64(1)
>  ans  =
>   230584300921369395*2*
>
> This was reported in 2018 @ http://bugzilla.scilab.org/15836 and is 
> still unfixed.
>
> For bitget, i will see how to do, if there is a workaround. If not, at 
> least warn users in the help page.
>
> Samuel
>
> Le 27/02/2020 à 16:58, Samuel Gougeon a écrit :
>> Le 27/02/2020 à 16:17, JLan a écrit :
>>> I wonder if i have misunderstood the documentation for bitget, or if 
>>> this is
>>> a bug? It seems to me that numbers > 2^53 are still not handled 
>>> correctly.
>>> --> a=uint64(2^61)
>>>   a  =   2305843009213693952
>>> --> b=uint64(2^61)+1
>>>   b  =   2305843009213693953
>>
>> bitget(b,1)
>>
>> --> bitget(b,1)
>>  ans  =
>>   0
>>
>> is a bug.
>> bitget.tst tests int64 and uint64 cases with other inttypes:
>> --> edit SCI\modules\elementary_functions\tests\unit_tests\bitget.tst
>>
>> When bitget() has been extended to 64 bits integers ~3 years ago, 
>> several bugs have appeared about the processing of these integers by 
>> other Scilab functions, noticeably some functions involved in the 
>> bitget implementation.
>> Not all are fixed (actually, only few of them are fixed).
>> But maybe it's another issue here. I could have a look, about this 
>> specific case.
>>
>> If you can do other tests and get issues, please report all of them 
>> on bugzilla.
>> Thanks
>>
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>
>
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