[ncl-talk] Minor concerns for the "num" function

[Rashed Mahmood]

Hi Rick,
Thanks for the answer.
I thought it should be 7, so that it is equal to the results from dimsizes.
But, of course, this is not a good comparison, comparing two different
functions.
I agree that it would consider 0 values as False, as is written in
documents.

Cheers,
Rashed







On Wed, Aug 14, 2019 at 3:55 PM Rick Brownrigg <brownrig at ucar.edu> wrote:

> Hi Rashed,
>
> It seems to me the functions are working as advertised, given that they
> are counting "true" values, not counting number of non-missing values. And
> as you likely know, its quite common in many programming languages (C/C++,
> Go, Python, Javascript) for a 0 value to represent boolean False, and
> anything non-zero to be True.
>
> In your example here:
>
> cd = (/9,10,0,0,0,5,8./)
>
> are you suggesting the answer should be 7 or 4?
>
> Rick
>
>
> On Wed, Aug 14, 2019 at 3:25 AM Rashed Mahmood via ncl-talk <
> ncl-talk at ucar.edu> wrote:
>
>> Hi All,
>> My concern is ignoring "0" when the num and it's relatives (dim_num*)
>> functions do a counting when NOT evaluating a certain condition.  I do know
>> that it is clearly written in the documents that "All numerical values *except
>> for 0* evaluate to True."
>>
>> My concern is that* if someone forgets about this "0" exception*, things
>> could go very wrong: Here is how:
>>
>> ab = fspan(0,30,20)
>>   print(num(ab)+" ... "+dim_num_n(ab,0)+" ... "+num(ab.ge.0)+" ...
>> "+dimsizes(ab))
>> (0) 19 ... 19 ... 20 ... 20
>>
>>   cd = (/9,10,0,0,0,5,8./)
>>   print(num(cd)+" ... "+dim_num_n(cd,0)+" ... "+dimsizes(cd))
>> (0) 4 ... 4 ... 7
>>
>> But these does not fail and give fatal error when used without any
>> condition, although there is not so helpful warning message. The concern is
>> that if these cannot provide right answer these must give error message
>> suggesting that 0 values occurred while counting or something similar?
>>
>>
>> Cheers,
>> Rashed
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