val = get(pmap, k)
So apparently, the concept definition actually requires that property maps are never const - which is admittedly a little weird.
It sounds like we're now on the same page! The above essentially means that it becomes literally impossible to write perfectly const-correct code (from a user standpoint). While const-incorrect code is bad enough, it also means that I may be missing out on potential compiler optimizations, that bugs me quite a bit more.
What may be done to remedy this?
I will admit that writing perfectly const-correct code can be very, very
difficult in many situations :) However, I'll defer to more experienced
Boosters with regards that its impossible. I will also say that
const-incorrect code isn't necessarily "bad". There are times that ignoring
const-ness is quite useful.
In this particular instance, I will cautiously say that the concept
definition is implemented incorrectly. If the constraints() funciton did
this:
property_map