Adding the ?. null verification

[Timon Gehr via Digitalmars-d]

On 06/18/2014 09:36 PM, H. S. Teoh via Digitalmars-d wrote:
> Here's a first stab at a library solution:
>
> 	/**
> 	 * Simple-minded implementation of a Maybe monad.
> 	 *

Nitpick: Please do not call it a 'Maybe monad'.
It is not a monad: It's neither a functor not does it have a μ operator. 
(This could be fixed though.) Furthermore, opDispatch does not behave 
analogously to a (restricted) monadic bind operator:

class C{ auto foo=maybe(C.init); }

void main(){
     import std.stdio;
     C c=new C;
     writeln(maybe(c).foo); // Maybe(Maybe(null))
}

The result should be Maybe(null), if the data type was to remotely 
resemble a monad.

Furthermore, 'Maybe' is a more natural name for a type constructor that 
adds an additional element to another type, and 'Maybe monad' in 
particular is a term that already refers to this different meaning even 
more strongly in other communities.