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E($n$;$F$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$if ($n$ =$_{0}$ 0) then $F$(null) else weighted{-}sum($p$;$\lambda$$x$.E($n$ {-} 1;rv{-}shift($x$;$F$))) fi 
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\\[0ex]{\em clarification:}
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\\[0ex]expectation($p$;$n$;$F$)
\\[0ex]$\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$\=if ($n$ =$_{0}$ 0)\+
\\[0ex]then $F$(null)
\\[0ex]else weighted{-}sum($p$;$\lambda$$x$.expectation($p$;$n$ {-} 1;rv{-}shift($x$;$F$)))
\\[0ex]fi 
\-\\[0ex]\emph{(recursive)}
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