between and among: worth Phobosization?

[Jerry]

Jerry <jlquinn at optonline.net> writes:

> Andrei Alexandrescu <SeeWebsiteForEmail at erdani.org> writes:
>
>> uint among(T, Us...)(T v, Us vals)
>> {
>>     foreach (i, U; Us)
>>     {
>>         if (v == vals[i]) return i + 1;
>>     }
>>     return 0;
>> }
>
> This seems less useful to me.  What was the example where you found it
> useful?

Being bad and following myself up...

I think this proposal is highlighting that Phobos more generally lacks
set operations.  It seems to me that among() is roughly equivalent to:

auto i = v in vals;

but this is only currently used for builtin hash tables.  Since this
syntax already exists, does it make sense to see if it can be done as
something like:

auto i = v in (val, val, val ...);

?

I've been playing with porting some code where we use hash tables and
sets quite a bit and end up creating a lot of bool[string] objects.  It
works, but I do wish there was a more explicit set.  This allows for
blah["entry"] = false, which isn't really what I'm trying to model :-)

Would it make sense to create a Set object in std.container?  

Jerry