Flag proposal

[Michel Fortin]

On 2011-06-11 09:05:52 -0400, "Steven Schveighoffer" 
<schveiguy at yahoo.com> said:

> As far as the negation, I think we need one more layer of type:
> 
> struct FlagParam(string pname)
> {
>     Flag!pname value;
>     alias value this;
>     this(Flag!pname x) { this.value = x }
>     FlagParam op???() const { return FlagParam(cast(Flag!pname)!value); }
> }
> 
> BTW, is there a way to hook "!"?  Maybe this won't work...  The idea is 
> to  have Yes.abc return FlagParam!"abc"(Flag!"abc".yes).

If you need to convert a bool to a Flag!"abc", you can do any of these:

	func(expression ? Yes.abc : No.abc);

or

	func(cast(Flag!"abc")expression);

or, with your proposal:

	func(FlagParam!"abc"(expression));

None of this is very appealing, but I find the first is the most readable.


-- 
Michel Fortin
michel.fortin at michelf.com
http://michelf.com/