From: ahoward <ahoward@...>
Date: 2003-06-24T06:40:54+09:00
Subject: Re: can't find appropriate regexp

On Mon, 23 Jun 2003, Simon Strandgaard wrote:

> Is there anyone who know how to do the *reject* thing ?

(?!pattern) rejects.

but as to the original problem:

the problem is that odd numbered escapes *contain* even numbered escapes and
vise versa, so you also need some sort of anchor ([^\\], ^, \A) etc.  but that
too becomes problematic... this seems to work because it handle odd number
escapes contained in even numbered escapes from being accepted - it other
words it forces odd numbered escapes to standalone :

~/eg/ruby > cat quotematch.rb
#!/usr/bin/env ruby
tests = DATA.readlines

re = %r/
  ["]
    (?:
      [^\\](?:[\\][\\])*[\\]["] | # prevent even escaped quotes
                                  # from being accepted for containing
                                  # and odd escaped quote

      (?:[\\][\\])*[\\]["]      | # accept odd escaped quotes

      (?:[\\])+[^"]?            | # accept any escape sequence which
                                  # does not escape a quote

      (?:[^\\"]+)                 # accept anthing neither quote nor escaped
    )*
  ["]
/iomx

tests.map{|t|f=nil;t.scan(re).map{|m| print"[#{m}] ";f=1;};puts if f}

__END__
foo "foobar";
bar "foo" "bar";
a "foo \"bar\"";
b "foo \\"bar\\"";
c "foo \\\"bar\\\"";
d "foo \\\\"bar\\\\"";
e "foo \t" "\t bar"
e "foo \\t" "\\t bar"

~/eg/ruby > ruby quotematch.rb
["foobar"]
["foo"] ["bar"]
["foo \"bar\""]
["foo \\"] [""]
["foo \\\"bar\\\""]
["foo \\\\"] [""]
["foo \t"] ["\t bar"]
["foo \\t"] ["\\t bar"]




-a
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  ====================================
  | Ara Howard
  | NOAA Forecast Systems Laboratory
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  | ~ > ruby -e 'p(%.\x2d\x29..intern)'
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