Introduction to Regular Expressions in Eiffel Programming Language
One of the rich and important ways of pattern matching and string manipulation in programming languages is
One of the rich and important ways of pattern matching and string manipulation in programming languages is
regular expressions are powerful tools for defining and applying patterns to manipulate and validate strings according to specified rules. These patterns, composed of literal characters and metacharacters, allow developers to perform complex string operations efficiently.
Eiffel regular expressions define patterns by literal characters like a, 1, @ and metacharacters like *, +,?, [ ] for classes of characters or quantifiers. This flexibility allows the fitting of strings against very diverse criteria.
For instance, in Eiffel, one uses the compile method of REGEXP to compile regular expressions. This method compiles a string pattern into a REGEXP object that will be used for subsequent matching operations. In such a case, compilation assures that a pattern is prepared to match efficiently against strings.
The class REGEXP proposes several methods to apply compiled regular expressions:
Beyond simple matching, Eiffel’s regular expressions offer facilities for really complex operations on strings, like the following:
Esample:
class
REGEXP_EXAMPLE
create
make
feature
make
local
regex: REGEXP
match_result: BOOLEAN
do
-- Define a regular expression pattern to match an email address
regex := REGEXP.compile ("^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$")
-- Check if a string matches the email pattern
match_result := regex.is_matching ("example@email.com")
if match_result then
io.put_string ("Valid email address%n")
else
io.put_string ("Invalid email address%n")
end
end
end
Expressiveness: They provide a concise syntax to specify complex patterns on strings.
Efficiency: Compiled regex patterns enable efficient operations for manipulating and validating strings.
Flexibility: They support quite a wide range of tasks beginning from simple validation up to complex text parsing and data extraction.
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