On Fri, Mar 25, 2011 at 2:58 AM, 7stud -- <bbxx789_05ss / yahoo.com> wrote:
> perl's regexes have a recursive feature, which can solve your problem.
> Want to call an external script?

Not necessary: Ruby has it, too.

irb(main):001:0> s="x(a(b)()c)y"
=> "x(a(b)()c)y"
irb(main):002:0> %r{(?<ne> \( (?:\g<ne>|[^()]+)* \) )}x.match s
=> #<MatchData "(a(b)()c)" ne:"(a(b)()c)">

irb(main):003:0> s = "f_(a)(x)=x^(2)+(5x//f'(x))"
=> "f_(a)(x)=x^(2)+(5x//f'(x))"
irb(main):004:0> s.scan %r{(?<ne> \( (?: \g<ne> | [^()] )* \) )}x
=> [["(a)"], ["(x)"], ["(2)"], ["(5x//f'(x))"]]

See http://www.geocities.jp/kosako3/oniguruma/doc/RE.txt

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/