From: Simon Strandgaard <neoneye@...>
Date: 2004-01-20T06:40:09+09:00
Subject: Re: regex help

On Tue, 20 Jan 2004 04:38:12 +0900, Chris Morris wrote:

> I need a re such that:
> 
>   '  /* comment */  String s = "***/";  '.gsub(re, "*\\")
> 
> returns:
> 
>   '  /* comment *\  String s = "***/";  '
> 
> I want to find all *\ instances that are not enclosed in double-quotes. 
> Or is this one of those problems ill-suited for a regex?


possible.. but difficult.

I spend this evening making some _broken_ experiments.

--
Simon Strandgaard


server> ruby test_main.rb
Loaded suite TestMain
Started
test_balance_bad1(TestMain): .
test_balance_bad2(TestMain): F
test_balance_bad3(TestMain): F
test_balance_ok1(TestMain): F
test_balance_ok2(TestMain): .

Finished in 0.030393 seconds.

  1) Failure:
test_balance_bad2(TestMain)
    [test_main.rb:25:in `assert_x'
     test_main.rb:33:in `test_balance_bad2']:
<["xx ", "*/"]> expected but was
<nil>.

  2) Failure:
test_balance_bad3(TestMain)
    [test_main.rb:25:in `assert_x'
     test_main.rb:37:in `test_balance_bad3']:
<["xx /* /* */ ", "*/"]> expected but was
<["/* /* "]>.

  3) Failure:
test_balance_ok1(TestMain)
    [test_main.rb:25:in `assert_x'
     test_main.rb:41:in `test_balance_ok1']:
<nil> expected but was
<["/*  "]>.

5 tests, 5 assertions, 3 failures, 0 errors
server> expand -t2 test_main.rb 
require 'test/unit'

class TestMain < Test::Unit::TestCase
  def mk_re
    comment_begin = '\/\*'   #   /*
    comment_end = '\*\/'     #   */
    re = / 
      ( 
        #{comment_begin} 
        .*?
      )
      #{comment_end}                   
      .*? 
      (?! #{comment_begin} )
      (?= #{comment_end} )
    /x
    re
  end
  def assert_x(expected, input)
    actual = mk_re.match(input)
    if actual
      actual = actual.to_a
      actual.shift
    end
    assert_equal(expected, actual)
  end
  def test_balance_bad1
    s = 'xx /* comment */  String s = "***/";  '
    assert_x(['/* comment '], s) 
  end
  def test_balance_bad2
    s = 'xx */ */ String s = "***/";  '
    assert_x(['xx ', '*/'], s)  
  end
  def test_balance_bad3
    s = 'xx /* /* */ */'
    assert_x(['xx /* /* */ ', '*/'], s)
  end
  def test_balance_ok1
    s = ' /*  */  /*   */ '
    assert_x(nil, s)  
  end
  def test_balance_ok2
    s = 'xx /* /* */ '
    assert_x(nil, s)   
  end
end

if $0 == __FILE__
  require 'test/unit/ui/console/testrunner'
  Test::Unit::UI::Console::TestRunner.run(TestMain, 3)
end
server>