Re: [Tarantool-patches] [PATCH 2/2] Add IsWhole method for checking the fractional part of a number

[Serge Petrenko <sergepetrenko@tarantool.org>]

07.06.2020 15:40, Chris Sosnin пишет:
> Thank you for the review!
>
>> On 6 Jun 2020, at 17:17, Serge Petrenko <sergepetrenko@tarantool.org> wrote:
>>
>> 05.06.2020 18:41, Chris Sosnin пишет:
>>> Currently there is no efficient way to do this.
>>>
>>> Needed for tarantool/tarantool#4415
>> Thanks for the patch!
>>> ---
>>>   decNumber.c | 30 ++++++++++++++++++++++++++++++
>>>   decNumber.h |  1 +
>>>   2 files changed, 31 insertions(+)
>>>
>>> diff --git a/decNumber.c b/decNumber.c
>>> index 7c53bc3..f4ad927 100644
>>> --- a/decNumber.c
>>> +++ b/decNumber.c
>>> @@ -501,6 +501,36 @@ uLong decNumberToUInt64(const decNumber *dn, decContext *set) {
>>>     return 0;
>>>     }  // decNumberToUInt64
>>>   +Flag decNumberIsWhole(const decNumber *dn) {
>>> +  const Unit *up=dn->lsu;
>>> +  if (dn->exponent>=0) {
>>> +    return 1;
>>> +    }
>>> +   else {
>>> +    Int count=-dn->exponent;
>>> +    // spin up whole units until reach the Unit with the unit digit
>>> +    for (; count>=DECDPUN; up++) {
>>> +      if (*up!=0) return 0;
>>> +      count-=DECDPUN;
>>> +      }
>>> +    if (count==0) return 1;             // [a multiple of DECDPUN]
>>> +     else {                             // [not multiple of DECDPUN]
>>> +      Int rem, theInt=0;                          // work
>>> +      // slice off fraction digits and check for non-zero
>>> +      #if DECDPUN<=4
>>> +        theInt=QUOT10(*up, count);
>>> +        rem=*up-theInt*powers[count];
>>> +      #else
>>> +        rem=*up%powers[count];          // slice off discards
>>> +        theInt=*up/powers[count];
>>> +      #endif
>>> +      if (rem!=0) return 0;
>>> +      up++;
>>> +      }
>>> +    }
>>> +    return 1;
>>> +  }  // decNumberIsWhole
>>> +
>> Consider this  diff:
>>
>> diff --git a/decNumber.c b/decNumber.c
>> index f4ad927..acc3fb1 100644
>> --- a/decNumber.c
>> +++ b/decNumber.c
>> @@ -515,17 +515,14 @@ Flag decNumberIsWhole(const decNumber *dn) {
>>         }
>>       if (count==0) return 1;             // [a multiple of DECDPUN]
>>        else {                             // [not multiple of DECDPUN]
>> -      Int rem, theInt=0;                          // work
>> +      Int rem;                          // work
>>         // slice off fraction digits and check for non-zero
>>         #if DECDPUN<=4
>> -        theInt=QUOT10(*up, count);
>> -        rem=*up-theInt*powers[count];
>> +        rem=*up-QUOT10(*up, count)*powers[count];
>>         #else
>>           rem=*up%powers[count];          // slice off discards
>> -        theInt=*up/powers[count];
>>         #endif
>>         if (rem!=0) return 0;
>> -      up++;
>>         }
>>       }
>>       return 1;
> I agree, looks much better, thanks!
> Applied on the branch.

Thanks for the fixes! Both patches LGTM.

>
>>>   /* ------------------------------------------------------------------ */
>>>   /* to-scientific-string -- conversion to numeric string               */
>>>   /* to-engineering-string -- conversion to numeric string              */
>>> diff --git a/decNumber.h b/decNumber.h
>>> index 85a3f3f..71ab27f 100644
>>> --- a/decNumber.h
>>> +++ b/decNumber.h
>>> @@ -169,6 +169,7 @@
>>>     decNumber  * decNumberTrim(decNumber *);
>>>     const char * decNumberVersion(void);
>>>     decNumber  * decNumberZero(decNumber *);
>>> +  uint8_t      decNumberIsWhole(const decNumber *dn);
>>>       /* Functions for testing decNumbers (normality depends on context)  */
>>>     int32_t decNumberIsNormal(const decNumber *, decContext *);
>> -- 
>> Serge Petrenko

-- 
Serge Petrenko