Examples
. My email address
ska@iitk.ac.in
. S = letter U {@, . }
. Letter a| b| .| z| A| B| .| Z
. Name letter +
. Address name '@' name '.' name '.' name
Now we look at the regular definitions for writing an email address ska@iitk.ac.in:
Set of alphabets being S = letter U {@, . } ):
Letter a| b| .| z| A| B| .| Z i.e., any lower case or upper case alphabet
Name letter + i.e., a string of one or more letters
Address name '@' name '.' name '.' name
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