What purpose to const besides functional programming?

[Walter Bright]

Jason House wrote:
> Simen Kjaeraas Wrote:
>> You are expecting invariant member functions to not do things they
>> can and should do.
> 
> My example was in response to Walter's statement (#5) that invariant
> objects can be accessed without synchronization.  I was providing a
> simple counter example.

The counter example was changing global state, not the invariant object. 
The statement #5 is correct - the counter example did not change the 
invariant object's state.