Digital Mars - digitalmars.D - Empty array vs. null array (WAS: Re: Arrays)

↑ ↓ ← → Bruno Medeiros <brunodomedeiros+spam com.gmail> writes:

Walter Bright wrote:
 2) An empty array is equal to a null pointer. Yikes!


 Not exactly, although a null array is also an empty array, the 




Really? So what exactly is the difference?

-- 
Bruno Medeiros - Software Developer, MSc. in CS/E graduate
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D

Apr 26 2008

↑ ↓ ← → "Janice Caron" <caron800 googlemail.com> writes:

On 26/04/2008, Bruno Medeiros <brunodomedeiros+spam com.gmail> wrote:
 Walter Bright wrote:
  >>
  >> 2) An empty array is equal to a null pointer. Yikes!
  >
  > Not exactly, although a null array is also an empty array, the reverse is
 not true.

  Really? So what exactly is the difference?


If (array.length == 0) then it's an empty array.
If (array.ptr == 0 && array.length == 0) then it's a null array.

Apr 26 2008

↑ ↓ ← → Bruno Medeiros <brunodomedeiros+spam com.gmail> writes:

Janice Caron wrote:
 On 26/04/2008, Bruno Medeiros <brunodomedeiros+spam com.gmail> wrote:
 Walter Bright wrote:
  >>
  >> 2) An empty array is equal to a null pointer. Yikes!
  >
  > Not exactly, although a null array is also an empty array, the reverse is
 not true.

  Really? So what exactly is the difference?

 If (array.length == 0) then it's an empty array.
 If (array.ptr == 0 && array.length == 0) then it's a null array.

True.
But that only makes an empty array not the *same* as a null array. They 
are still equal (in terms of equality, think of the equality operator), 
which I believe is what the original poster was thinking about, and I 
agree. Since Walter refuted that by saying "Not exactly", I was trying 
to learn why, but probably Walter just misunderstood the OP.

-- 
Bruno Medeiros - Software Developer, MSc. in CS/E graduate
http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D

Apr 26 2008