Closure under prefix operator. Prefix operator is defined as: prefix(w E E*) = {w1 wk| 0

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Extracted text: Closure under prefix operator. Prefix operator is defined as: prefix(w E E*) = {w1 wk| 0 < k="">< jw]}.="" for="" example,="" if="" a="" string="" w="asu," prefix(w)="{e,a," as,="" asu}.="" show="" prefix(l)="" {prefix(w)|="" w="" e="" l}="" is="" a="" cfl="" if="" l="" is="">