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Re: !null values in arrays [message #74040]

Thu, 16 December 2010 07:39

penteado
Messages: 866
Registered: February 2018

Senior Member
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On Dec 16, 1:14 pm, Paul van Delst <paul.vande...@noaa.gov> wrote:
> Purely for perspective into the issue, ruby handles operations with null values thusly:
>
> irb(main):001:0> 3 + nil
> TypeError: nil can't be coerced into Fixnum
> from (irb):1:in `+'
> from (irb):1
>
> and python similarly:
>
>>>> 3 + None
>
> Traceback (most recent call last):
> File "<stdin>", line 1, in ?
> TypeError: unsupported operand type(s) for +: 'int' and 'NoneType'

Both appropriate. !null and NaN are not the same, and are not the same
as 0. In fact, their lack in more primitive languages is an important
hassle.

0 is not, intrinsically, the same as missing data. In particular, most
mathematical operations on NaNs (say, adding a value to a NaN) should
always return NaN to make sense. If an array has missing data, data
cannot be magically created on the missing elements because, say, a
scalar was added to the array.

NaN is special in the sense that it is a floating point value, part of
the IEEE 754 standard, and properly recognized by hardware and other
software. !null is a language construct, which necessarily varies
among languages, as they vary in what constitutes a variable. It is an
undefined variable, so one can assign to it, but not operate on it,
the same way that one cannot operate on an undefined variable, but can
create it by assignment.

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[Message index]

		Re: !null values in arrays By: penteado on Thu, 16 December 2010 07:39
		Re: !null values in arrays By: Paul Van Delst[1] on Thu, 16 December 2010 07:14
		Re: !null values in arrays By: Axel Martínez on Thu, 16 December 2010 03:30
		Re: !null values in arrays By: David Fanning on Wed, 15 December 2010 10:20

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