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Tue Aug 4 20:32:34 CEST 2009

Continuations

So.. ISWIM uses n-ary primitive application, but unary abstraction and
application.  Why is this?  It seems that it makes the extension of
the environment on application easier: only a single variable has to
be added.

Maybe this isn't necessary for Scheme.  A multivalued application adds
all variables at the same time.  Instead of arg,fun,opd as explained
in PLLC, I needs just a single type that evaluates all variables in an
application from left to right, starting with the function position,
and then performs either an application (extending the environment) or
a primitive evaluation (production of a value).

So how to represent (x x x _ x x x) where "_" is the hole?

In short: what does the CEKS machine do?

   It converts the current expression and its continuation in a
   simplified expression and an updated continuation.  It is
   _application_ (triggered by the availability of the last argument)
   that _pops_ the K stack.

So.. Representing continuations.

(((f a b) E) K) -> ( _ (((f E) (a E) (b E)) K))
                -> ((f E) (((a E) (b E)) K))




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