Balanced brackets: Difference between revisions

=={{header|Ruby}}==

{{trans|D}}

{{works with|Ruby|1.9}}

<lang ruby>re = /\A # beginning of string

(?<bb> # begin capture group <bb>

\[ # literal [

\g<bb>* # zero or more <bb>

\] # literal ]

)* # end group, zero or more such groups

\z/x # end of string

(0..9).each do |i|

s = "[]" * i

# Knuth shuffle

(s.length - 1).downto(1) do |a, b|

b = rand(a + 1)

s[a], s[b] = s[b], s[a]

end

puts((s =~ re ? " OK: " : "bad: ") << s)

end

["[[]", "[]]", "[letters]"].each do |s|

puts((s =~ re ? " OK: " : "bad: ") << s)

end</lang>

One output: <pre> OK:

OK: []

bad: ][][

bad: ]][[][

bad: ]][[][[]

bad: ]][[[[]][]

bad: ][][]]][[[[]

OK: [[]][[[]]][][]

bad: [[][][][]]][[][]

bad: []]][]][[][[[][][]

bad: [[]

bad: []]

bad: [letters]</pre>