re = /# Define the opening and closing elements before the recursion occurs
(?(DEFINE)
(?<open_curly>\{)
(?<close_curly>\})
(?<open_square>\[)
(?<close_square>\])
(?P<open_pascal>(?i:\bbegin\b))
(?P<close_pascal>(?i:\bend\b))
(?P<open_lua>--\[)
(?P<close_lua>--\])
(?<open>\g'open_curly'|\g'open_square'|\g'open_pascal'|\g'open_lua')
(?<close>\g'close_curly'|\g'close_square'|\g'close_pascal'|\g'close_lua')
)
# Match the opening element
(\g'open'
(?>
# For recursion, don't match either the opening
# or closing element
(?!\g'open'|\g'close')(.)
|
# Recurse this captured pattern
(?-1)
)*
# Match the closing element
\g'close')
/x
str = 'EVENLY BALANCED curly braces
{{{}}}
{ test1 { test2 { test3 { test4 } } } }
UNEVENLY BALANCED curly braces
{{{{}}}
{ test1 { test2 { test3 { test4 } } } } }
MULTI-LINE EVENLY BALANCED curly braces
{
}
MULTI-LINE UNEVENLY BALANCED curly braces
{{
}
EVENLY BALANCED square braces
[ test1 [ test2 [ test3 [ test4 ] ] ] ]
EVENLY BALANCED square and curly braces
{ test1 [ test2 { test3 [ test4 ] } ] }
UNEVENLY BALANCED square and curly braces
{ test1 [ test2 { test3 [ test4 ] } } ]
'
# Print the match result
str.scan(re) do |match|
puts match.to_s
end
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html