CODEWITHSUNDEEP
eiffel
Pipo
Pipo

Reputation: 5093

Eiffel: regular expressions how to do grouping

I'd like to do grouping of regular expressions with eiffel. How do I do something like

l_reg.compile ("^([0-9]{3}) (rabbit[0-9]).*")
l_groups := l_reg.groups ("123 rabbit1")
my_first_rabbit := l_groups.at (2)

Didn't find any example on groups, LX_DFA_REGULAR_EXPRESSION class and other googlings

Upvotes: 0

Views: 62

Answers (1)

Eric Bezault
Eric Bezault

Reputation: 141

One solution is to use RX_PCRE_REGULAR_EXPRESSION instead of LX_DFA_REGULAR_EXPRESSION:

Including $ISE_LIBRARY\contrib\library\gobo\library\regexp\src\library.ecf library

l_reg: RX_PCRE_REGULAR_EXPRESSION
...
l_reg.compile ("^([0-9]{3}) (rabbit[0-9]).*")
l_reg.match ("123 rabbit1")
my_first_rabbit := l_reg.captured_substring (2)

There is no groups routine, although it could be implemented by calling captured_substring internally. There is only a routine split which does the reverse: returns the substrings which did not match the regular expression.

Something like

    regex_groups (a_haystack, a_needle: STRING): ARRAY[STRING]
            -- Test with https://www.regextester.com/1911
        require
            regex_match (a_haystack, a_needle)
        local
            l_reg: RX_PCRE_REGULAR_EXPRESSION
            l_index: like {RX_PCRE_REGULAR_EXPRESSION}.match_count
        do
            create Result.make_empty
            create l_reg.make
            l_reg.compile (a_needle)
            if l_reg.is_compiled then
                l_reg.match (a_haystack)
                from
                    l_index := 1
                until
                    l_index > l_reg.match_count
                loop
                    Result.extend (l_reg.captured_substring (l_index))
                    l_index := l_index + 1
                end
            else
                --- error compiling regex
                fallible.set_last_error (create {SIT_INTERNAL_ERROR}.make ("regex_group-> regex does not compile:" + a_needle))
            end
        ensure
            not fallible.has_error
            instance_free: Class
        end

you could test your regex here: https://www.regextester.com/1911

Upvotes: 1

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