COMPUTER SCIENCE AND ENGINEERING
COMPILER DESIGN
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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x? in a regular expression denotes
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only x
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only epsilon
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either x or epsilon
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None of the above
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Explanation:
Detailed explanation-1: -Matches a single Unicode grapheme, whether encoded as a single code point or multiple code points using combining marks.
Detailed explanation-2: -epsilon which denotes the empty string containing no characters. null which denotes the empty set of strings.
Detailed explanation-3: -Base Rule 1: Epsilon is a regular expression that stands for the the empty string.
Detailed explanation-4: -A regular expression (shortened as regex or regexp; sometimes referred to as rational expression) is a sequence of characters that specifies a search pattern in text. Usually such patterns are used by string-searching algorithms for “find” or “find and replace” operations on strings, or for input validation.
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