arrays: if(null == [ ])

[Gor Gyolchanyan]

At least we could make an empty string a null array of characters for
consistency. How many times did anyone use the feature of string literals
being null-terminated?

On Mon, May 14, 2012 at 8:56 PM, Jonathan M Davis <jmdavisProg at gmx.com>wrote:

> On Monday, May 14, 2012 14:08:17 Gor Gyolchanyan wrote:
> > Hi! I have a small question:
> > Is the test for a null array equivalent to a test for zero-length array?
> > This is particularly interesting for strings.
> > For instance, I could return an empty string from a toString-like
> function
> > and the empty string would be printed, but If I returned a null string,
> > that would indicate, that there is no string representation and it would
> > cause some default string to be printed.
> > So, the question is, if a null array is any different from an empty
> array?
>
> A null array is equal to an empty array.
>
> assert(null == []);
> assert(null == "");
>
> It's when you use is that things change. An array "is null" only if it's
> ptr
> property is null, which is true only for uninitialized arrays and [] (the
> compiler doesn't bother allocating memory for [], so it's basically the
> same
> as null). However, since "" is a string literal, it _does_ have memory
> allocated to it, so
>
> assert([] is null);
> assert("" !is null);
>
> So, it all comes down to the ptr property. An array is considered to have a
> length of 0 if its length property is 0 (which null arrays do). It's only
> considered to be null if its ptr property is null. == uses the length
> property, ignoring the ptr property as long as the lengths are equal (and
> checking each of the elements refered to by the ptr property if the lengths
> aren't equal), whereas is specifically checks whether the ptr properties
> of the
> two arrays are equal.
>
> Personally, I think that conflating null and empty like this is atrocious,
> but
> that's how the language works, and we're stuck with it.
>
> - Jonathan M Davis
>



-- 
Bye,
Gor Gyolchanyan.
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