[Haskell-beginners] fixpoint operator for ULC with specific reduction property

ben benedikt.ahrens at gmx.net
Thu Nov 4 06:43:08 EDT 2010


I'm looking for a fixpoint operator Z for the untyped lambda calculus
that has the property

Z g --> g (Z g)

for any g.

The best-known fixpoint operator Y := \f. (\x. f (x x)) (\x. f (x x))
does not have this property, but only

Y g --> T <-- g (Y g)

for some T.

Does anybody know such a Z I'm looking for?


ps. Please keep me in CC, since I'm not currently subscribed to the list.

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