Head Const

[Walter Bright via Digitalmars-d]

rears its head again :-)

Head Const is what C++ has for const, i.e. it is not transitive, applies to one 
level only. D has transitive const.

What head const will do for us:

1. make it easy to interface to C++ code that uses const, as currently it is not 
very practical to do so, you have to resort to pragma(mangle)

2. supports single assignment style of programming, even if the data is 
otherwise mutable

The downside is, of course, language complexity.