Semantics of ==

[Isaac To]

>>>>> "Axel" == Axel Boldt <axelboldt at yahoo.com> writes:

    Axel> l=[] l.append(l) Is l well-founded? Both answers "yes" and "no"
    Axel> are consistent with the above definition. If you write a program
    Axel> to determine whether a given list is well-founded, it will run
    Axel> into an infinite loop.

That depends on how you write the program.  I can easily give you a program
that will tell you either this is or is not, depending on whether you like
it one way or the other---provided that I have a little bit of memory to
play with, or I'm allowed to look at my own back-trace.

Regards,
Isaac.