Tom Lane wrote:
>Greg Stark <gsstark@mit.edu> writes:
>
>
>>Alvaro Herrera <alvherre@dcc.uchile.cl> writes:
>>
>>
>>>Hmm. Well, it showed the multiple incorrect uses of 0 as NULL in
>>>dllist.c and other places,
>>>
>>>
>
>
>
>>Incidentally, while it may not be conformant to your style guidelines, use of
>>the constant 0 compared to or assigned to a pointer is a perfectly valid ANSI
>>spelling for NULL.
>>
>>
>
>Absolutely. But I agree that it is more readable to use NULL when you
>mean a null pointer, and 0 when you mean an integer zero. The C
>standard may not distinguish these concepts, but I do ;-)
>
>Something that I don't have a real strong feeling about is
> if (ptr != NULL)
>versus
> if (ptr)
>I've been known to write both. Can anyone mount a good readability
>argument for one over the other?
>
>How about the inverse case,
> if (ptr == NULL)
>versus
> if (!ptr)
>Applying a boolean ! to a pointer seems a bit shaky to me, though
>it's certainly a common locution.
>
>
>
>
If we allow "if (ptr)" then allowing the inverse to be "if (! ptr)"
seems logical enough. As you say, it's a very common idiom, and allowing
one without the other would be rather non-orthogonal.
cheers
andrew