Just a friendly reminder about using arrays in boolean conditions

[Dom DiSc]

On Monday, 18 November 2024 at 12:24:01 UTC, user1234 wrote:
>> ```d
>> void v(string s)
>> {
>>     if (s.length)           writeln("case length :`", s, "`");
>>     else if (s is null)     writeln("case null :`", s,  "`");
>>     else                    writeln("case not null but no 
>> length:`", s,  "`");
>> }

One should always first check for null and then for length. This 
should be immediately clear, as asking for a length doesn't make 
sense if something is null.
Ok, an array has both a pointer and a length, but I would never 
expect the length to contain something useful, if the pointer is 
not assigned a legal address.
If I were to implement arrays, I would use a simple pointer, and 
length would be the first element of the allocated block. For any 
object, I have always in mind that it could be implemented in 
this way, so would never access anything as long as the pointer 
is not checked first.