Join the social network of Tech Nerds, increase skill rank, get work, manage projects...
 
  • Operations of character classes and use with quantifier

    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 175
    Comment on it

    Dear readers in previous blog I have explained about the character classes(basic definition). Now in this tutorial I am going to explain all of you about operations of character classes with Unions, Intersections, Subtractions and how we can use character classes with quantifiers.

     

    Unions of character classes:

      Single character class containing 2 or more character classes is called as Union of character classes . For creating a Union, we have to nest one character class inside the other character class.

    Eg : [a-f[x-z]]. This union character class matches the letters a,b,c,d,e,f,x,y and z.

                                

     Enter the regex: [a-f[x-z]]

     Enter input string to search: y

    I found the letter "y" starting at index 0 and ending at index 1.

     

     Enter the regex: [a-f[x-z]]

     Enter input string to search: k

    No match found.

     

    Intersection of character classes:

    Single character class containing 2 or more character classes inside one class with the use of && between 2 character classes, hence it is called as intersection of character classes . It will match the characters which are common to all character classes.

    Eg: [a-z && [abc]]. This intersection character classes matches the letters only a,b and c.

     

    Enter the regex: [a-z && [abc]]

    Enter input string to search: c

    I found the letter "c" starting at index 0 and ending at index 1.

     

    Enter the regex: [a-z && [abc]]

    Enter input string to search: f

    No match found.

     

    Enter the regex: [0-9 && [3-8]]

    Enter input string to search: 5

    I found the digit "5" starting at index 0 and ending at index 1.

     

    Enter the regex:  [0-9 && [3-8]]

    Enter input string to search: 2

    No match found.

     

    Subtraction of character classes:

      Single character class containing 2 or more character classes inside one class with the use of && between 2 character classes and use of ^ in other nested character class, it is called as subtraction of character classes . It will match the characters except that characters which are available in other character class.

    Eg: [a-z && [^abc]]. This subtraction character classes matches the letters except abc.

     

    Enter the regex: [a-z && [^abc]]

    Enter input string to search: t

    I found the letter "t" starting at index 0 and ending at index 1.

     

    Enter the regex: [a-z && [^abc]]

    Enter input string to search: b

    No match found.

     

    Use of character classes and capturing groups with quantifier:

      If regular expression is ‘xyz+’ means it will match x followed by y followed by z one or more times means we can attach a quantifier not only on a single character also attach on a character classes and capturing group such as [xyz]+ , it will match x or y or z one or more times and if regular expression is (xyz)+ , it will match the group (x followed by y followed by z) one or more times.

     

    Eg:  Enter the regex: (sri){3}

            Enter input string to search: srisrisrisrisrisri

    I found the text “srisrisri” starting at index 0 and ending at index 9.

    I found the text “srisrisri” starting at index 9 and ending at index 18.

     

          Enter the regex: sri{3}

          Enter input string to search: srisrisrisrisrisri

    No match found.

     

    In the first example quantifier applies to the entire capturing group sri means s followed by r followed by i 3 times, it will match to the input string, Hence the result will be true.

    In the second example remove the parenthesis then regex will s followed by r followed i, here i is 3 times and it will match to the input string, Hence the result will be false.

 0 Comment(s)

Sign In
                           OR                           
                           OR                           
Register

Sign up using

                           OR                           
Forgot Password
Fill out the form below and instructions to reset your password will be emailed to you:
Reset Password
Fill out the form below and reset your password: