How useful should inout be?

[Kagamin]

On Sunday, 23 March 2014 at 10:28:54 UTC, Infiltrator wrote:
> So, is this a limitation with inout, part of its design, or am 
> I misunderstaning something more fundamental?

It's fundamental: inout makes sense for function attributes only 
and can't be used as a template parameter or struct/class field 
(what map attempts). Opaque template parameters would solve the 
issue and can be also used for other purposes, but on the first 
sight they seem like a task of galactic scale, hence nonviable.