Probable C# 6.0 features

[Robert Clipsham]

On Tuesday, 10 December 2013 at 23:53:25 UTC, Ary Borenszweig 
wrote:
> On 12/10/13 5:35 PM, Namespace wrote:
>> I love Monadic null checking. Would be great if D would have 
>> it.
>
> What does a monad have to do with that?
>
> (just out of curiosity... BTW, the other day I friend tried to 
> explain me monads and he realized couldn't understand them 
> himself)

Monads suffer from the same problem algebra, templates and many 
other things do in that they have a scary name and are often 
poorly explained.

They way I like to think of monads is simply a box that performs 
computations. They have two methods, bind and return. return lets 
you put a value into the box, and bind lets you call some 
function with the value that's in the box. Probably the simplest 
example is the maybe monad ("monadic null checking"). The idea is 
to let you change something like this:
----
auto a = ...;
if (a != null) {
     auto b = a.foo();
     if (b != null) {
         b.bar();
         // And so on
     }
}
----
Into:
----
a.foo().bar();
----

Here, the bind and return methods might look something like:
----
// "return" function
Maybe!Foo ret(Foo f) {
     return just(f);
}
auto bind(Maybe!Foo thing, Foo function(Foo) fn) {
     if(thing) {
         return ret(fn(thing));
     }
     return nothing();
}
----
There are two functions here for getting instances of maybe - 
nothing and just. Nothing says "I don't have a value" and just 
says "I have a value". The bind method then simply says "if I 
have a value, call the function, otherwise just return nothing". 
The code above would be used as follows:
----
bind(bind(a, &foo), &bar);
----
With a bit of magic you can get rid of the overhead of function 
pointers and allow it to work with other function types, but it 
shows the general concept - wrap up the values, then use bind to 
chain functions together.

The ?. operator mentioned in the article is simply some syntactic 
sugar for a monad, hence "monadic null checking".