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  \textbf{CS 319 -- The Lambda Calculus}\\
  \textbf{Assignment 4, Winter 2000}\\
  Due Monday, 14 February\\
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\item Define a natural version of sharing in the lambda calculus,
where residuals are initially shared, and portions of a term are
copied only when it appears to be necessary. Show that there is no
effective optimal strategy for beta reduction in this version of the
lambda calculus with sharing.
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\item Give an example where optimal shared reduction in the combinator 
calculus does not correspond to optimal shared reduction in the lambda 
calculus.
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