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Regular expression

AsifAliAsifAli Member Posts: 39
can any define me simply wat is regular expression how they work n how to solve n how to use..

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  • jeffpostjeffpost Member Posts: 316
    : can any define me simply wat is regular expression how they work n how to solve n how to use..
    :
    Formal definition:

    The symbols that appear in regular expressions are the letters of the alphabet, the symbol for the null string, parentheses, the star operator, and the plus sign.

    The set of regular expressions is defined by the following rules:
    Rule 1 Every letter of the alphabet can be made into a regular expression by writing it in boldface; the null string is a regular expression.
    Rule 2 If r1 and r2 are regular expressions, then so are:
    (r1)
    r1r2
    r1 + r2
    r1*
    Rule 3 Nothing else is a regular expression.

    Regular expressions are used in compilers and other programs for scanning, parsing, etc.

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