SYNTAX ANALYSIS
ROLE OF THE PARSER
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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zero or more occurrences of a and b
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zero or more occurrences of a or b
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one or more occurrences of a and b
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letter a followed by zero or more occurrences of b
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Detailed explanation-1: -a*b* corresponds to the set of strings consisting of zero or more a’s followed by zero or more b’s. a*b+a* corresponds to the set of strings consisting of zero or more a’s followed by one or more b’s followed by zero or more a’s.
Detailed explanation-2: -A regular expression followed by an asterisk ( * ) matches zero or more occurrences of the regular expression. If there is any choice, the first matching string in a line is used. A regular expression followed by a plus sign ( + ) matches one or more occurrences of the one-character regular expression.
Detailed explanation-3: -Hence a string of L consists of zero or more aab’s in front and zero or more bb’s following them. Thus (aab)*(bb)* is a regular expression for L.
Detailed explanation-4: -In regular expressions, asterisk (*) means “match zero or more of the preceding character.” To make a “wildcard” (that is, an expression that matches anything) with regular expressions, you must use ‘. *’ (dot asterisk). This expression means, “match zero or more of any character.”