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

[Chris Sosnin <k.sosnin@tarantool.org>]

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.

> 
>>  /* ------------------------------------------------------------------ */
>>  /* 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