Regular Expressions in Eiffel Programming Language

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 Regular Expressions in Eiffel Programming Language not exempted. In Eiffel, regular expression processing is handled through class REGEXP of library EiffelBase. It provides methods to compile, match, or manipulate strings based on specified patterns.

What is Regular Expressions in Eiffel Programming Language?

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.

Key Features of Regular Expressions in Eiffel:

Pattern definition and composition

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.

Pattern compilation

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.

Matching Operations

The class REGEXP proposes several methods to apply compiled regular expressions:

• is_matching(string: STRING): It verifies whether a given string matches the compiled regex pattern. Returns a boolean result, True for a match and otherwise False.
• match(string: STRING): Finds the first occurrence of the regex pattern in the string and returns information about the matched substring.
• search(string: STRING): It finds the starting position of the first occurrence of the regex pattern in a string.

STRING MANIPULATION:

Beyond simple matching, Eiffel’s regular expressions offer facilities for really complex operations on strings, like the following:

• Validation: checking that strings respect predefined formats, including for e.g. Email addresses or Phone numbers.
• Extraction: Extracting relevant data from Text with predefined patterns.
• Substitution: Trying replacing parts of strings that do respect predefined patterns by another content.

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

Advantages of Using Regular Expressions in Eiffel

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.