On 26.09.2011 08:32, Jonathan M Davis wrote:
On Monday, September 26, 2011 08:14:31 Rainer Schuetze wrote:
Which finally brings us back to the original question: What does
immutable guarantee in the face of non-pure property getter functions?
immutable guarantees that when an object is immutable, none of its member
variables will _ever_ be altered. It guarantees _nothing_ about variables
external to the object, and impure function can access pretty much anything
external to an object via module level or static functions or variables, so an
impure function could return literally _anything_ and could vary on every call
even if the object is immutable. Any impure member function which uses values
external to the object has to worry about the thread-safety of those values.
The thread-safety of the object itself is guaranteed, but that's all.
- Jonathan M Davis
Thanks for clarifying. My conclusion still is: if the immutable data
structure implementation is unknown or complex enough that you cannot
make sure the implementation of property getters are not screwed up, you
are relying on faith similar to head const in C++.
