From: Tom Cloyd <tomcloyd@...>
Date: 2009-02-08T05:50:01+09:00
Subject: Re: cannot remove multiple space> nuts!

David A. Black wrote:
> Hi --
>
> On Sat, 7 Feb 2009, Tom Cloyd wrote:
>
>> Tom Cloyd wrote:
>>> I'm baffled by this strange outcome - I cannot reduce multiple 
>>> spaces from a text file. This isn't just a regex problem, somehow. 
>>> I'm failing to grasp something essential, but don't know what it is. 
>>> All help appreciated, as usual!
>>>
>>> Here is a demo of my problem, in which I try two different ways, and 
>>> both fail:
>>>
>>> === code ===
>>> # h2t.rb
>>>
>>> def main
>>>  # conversion table spec
>>>  conv = [
>>>  [ '<h1>', 'h1. ' ], [ '<h2>', 'h2. ' ], [ '<h3>', 'h3. ' ],
>>>  [ '<h4>', 'h4. ' ], [ '<h5>', 'h5. ' ], [ '<h6>', 'h6. ' ],  [ 
>>> /<\/h\d>/, '' ],
>>>  [ " +", ' ' ]]  # <= this last array element should do the trick, 
>>> but doesn't
>> Ouch. THIS - [ / +/, ' ' ], substituted for [ " +", ' ' ] above fixes 
>> it. I'm going blind, obviously.
>
> Just for fun, here's another way to write the method:
>
> def main
>  data = File.read("tom.txt")
>  data.gsub!(/<(h[1-6])>/, "\\1. ")
>  data.gsub!(/<\/h\d>/, "")
>  data.squeeze!(' ')
>
>  open("tom.out", "w") {|f| f.write(data) }
>
> end
>
> I think that does the same thing. Tweak to taste :-)
>
>
> David
>
That's beautifully economical, and reveals a far better grasp of regex 
than I was able to attain last night. However, I'm having trouble with 
this line:

data.gsub!(/<(h[1-6])>/, "\\1. ")

It certain works, but I don't grasp the "\\1. " part. I haven't yet 
found anything that might shed light on this magic. How does it retain 
the 'h' and whatever digit follows it? It looks somehow like "\\" == 
retain matched alpha, and the "1" does the same for matched digits, but 
I really haven't a clue. Can you elucidate just a bit?

Thanks!

Tom

-- 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tom Cloyd, MS MA, LMHC - Private practice Psychotherapist
Bellingham, Washington, U.S.A: (360) 920-1226
<< tc@tomcloyd.com >> (email)
<< TomCloyd.com >> (website) 
<< sleightmind.wordpress.com >> (mental health weblog)
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