Flag proposal

[so]

>> My take on this is that we shouldn't try to reinvent the boolean in the
>> standard library.
>
> I think this characterization is wrong. Let me replace the meaningless  
> Abc with an actual example, e.g. OpenRight in std.algorithm.
>
> OpenRight is not a Boolean. Its *representation* is Boolean. It is  
> categorical data with two categories. You can represent it with an  
> unstructured Boolean the same way you can represent an automaton state  
> with an unstructured integer or temperature with an unstructured double,  
> but then you'd have the disadvantages that dimensional analysis  
> libraries are solving.

Quite contrary i think it is pretty much spot on, if it is not but just  
its representation is boolean so is every other usage of boolean.

The only reason we use an enum instead of simple bool is self  
documentation "fun(OpenRight.yes)". You simply can't deny the named  
arguments solve not only this particular issue but the entire area nicely  
"fun(openRight:true, width:4, height:3, depth:5)".