Re: RFC 118 (v1) lvalue subs: parameters, explicit assignment, andwantarray() changes

[Nathan Torkington]

Hildo Biersma writes:
> Hold on - post conditions are not intended to veto a change, they're
> intended to terminate the program if an assertion is invalid.  Hence it
> should not matter if they run before or after assignment.
> 
> Given that the assertion should be "now this and that should be true",
> and you may want to call validation methods as part of that assetion,
> the implementation of the checks becomes vastly easier if they are
> applied to the new state of the object, instead of the old state and a
> set of proposed changes.

So it sounds like Damian's lvalue subs + postconditions won't give
me what I want.  How do I do what I want?  Have an lvalue sub but
prevent the value from being changed to something invalid?

Do I need a combination of lvalue subs and tied variables?  Augh.

Nat