foreach, is and pointer

[rikki cattermole via Digitalmars-d-learn]

On 26/03/2017 7:52 AM, helxi wrote:
> What's the difference between
> 1.
> string x = "abcd";
>     foreach(character; x)
>         write(character);
>
> and
>
> string x = "abcd";
>     foreach(character; x[0..$])
>         write(character);

Hopefully the compiler is smart enough to ignore that slice (since its 
identical in purpose).

> 2. is and ==

is: bit for bit comparison
==: "magic" comparison logic, supports e.g. opEquals on classes.

> 3. pointer and address and reference?

pointer: a place in memory! or hdd.. or well pretty much anywhere the 
kernel maps it to, just assume that there is some data there that you 
may be able to do some, all or none of these things read, write, 
execute. May also be invalid aka null aka 0.

reference: pointer + some other pointer generally, e.g. class instance 
data pointer + typeinfo reference + vtable.