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

[Rick Brownrigg]

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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