[Python-3000] Type Comparisons with Godel Numbers

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    Giovanni> One way would be to keep boolean flags like "is this a list of
    Giovanni> integers". It could be updated after each list modification,
    Giovanni> so that typechecks come for (almost) free.

Where would that be done?  If it's in the untyped function in Guido's
example, how does it know it's supposed to be a list of ints?  If it's in
the typed function the untyped function calls, it seems to me you'll have to
do the entire check of a million elements before any user code is executed
to raising a typecheck error after partial execution someone else brought
up.

Other (difficult or unworkable I think) alternatives:

* Require that typed functions may only be called by other typed functions.
  That way lies madness I think.  It seems to me like it would be similar to
  the "const" virus in ANSI C.

* Allow lazy type checking, but implement some sort of transaction that is
  only committed if the typed function executes successfully.  (More
  madness.  I know!  Implement the virtual machine objects in a database!
  Tell the Jython and IronPython folks to suck rocks!)

Then again, perhaps brighter folk will think of something that will actually
work.  (I'm happy to live without type annotations, but that's just me.)

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