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Definition of re

Definition of re. Let Sigma be a given alphabet. Then. 1 .  ,  , and a   are all regular expressions. These are called primal regular expressions . 2 . If r 1 and r 2 are regular expressions, so are r 1 + r 2 , r 1 . r 2 , r 1 *, and (r 1 ).

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Definition of re

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  1. Definition of re Let Sigma be a given alphabet. Then 1. , , and a  are all regular expressions. These are called primal regular expressions. 2. If r1 and r2 are regular expressions, so are r1 + r2, r1. r2, r1*, and (r1). 3. A string is a regular expression if and only if it can be derived from the primitive regular expressions by a finite number of applications of rules in (2). union of two re’s is a re concatenation of two re’s is a re closure of a re’s is a re a re may be parenthesized

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