What Does @ Mean?

[Alex]

On Monday, 8 April 2019 at 11:58:49 UTC, Ron Tarrant wrote:
> This is frustrating and makes me feel like a complete newb. 
> Worse, it's impossible to search for. Ever try Googling a 
> single character?
>
> The D documentation also doesn't seem to explain the meaning of 
> this or any other token. Sure, most of them are obvious, but 
> this one eludes me. All I can find is this: 
> https://dlang.org/spec/lex.html#tokens
>
> Would someone please tell me what an at sign (@) means when 
> it's used like this:
>
> bool isLeaf() @property
> {
>    return children.length == 0;
> }
>
> In fact, I have no idea what @ means anywhere other than in an 
> email address. Is this a common thing in contemporary languages?
>
> And while I'm asking, does an underscore have special meaning 
> when used either at the beginning or end of a variable name?
>
> How about a double underscore?
>
> I know underscores are sort of left over from C, but do these 
> characters have special meaning in D or are they simply a 
> convention... like T in a template definition?

Some of the attributes in D go with an "@".

https://forum.dlang.org/post/fiwfcsqmjsndcjixipgz@forum.dlang.org
https://wiki.dlang.org/Language_Designs_Explained
https://dlang.org/spec/attribute.html