From: "Bermejo, Rodrigo" <rodrigo.bermejo@...>
Date: 2003-04-24T09:03:31+09:00
Subject: Re: grep and regular expressions in ruby

I widely  recommend you (if you are a newbie) the 'Sam's Teach Yourself 
Ruby in 21 days '  book.....
a good and enjoyable reading ....
I read it in just 18 days(..may I forgot some chapters ?) ....and it's 
still in my desktop

Take a look at:

http://www.bookpool.com/.x/mprew9z9y1/ss/1?qs=ruby

They use to have good prices.

-r.
Novody is perfect.
------------------>

Krishna Dole wrote:

>Thanks Bermejo and Daniel.
>It would be nice to have negation in REs and a more flexible grep, but I
>will get by fine using select.
>
>I've been meaning to purchase The Ruby Way... maybe tonight.
>
>Thanks again,
>Krishna
>
>-----Original Message-----
>From: Daniel Carrera [mailto:dcarrera@math.umd.edu]
>Sent: Wednesday, April 23, 2003 4:28 PM
>To: ruby-talk ML
>Subject: Re: grep and regular expressions in ruby
>
>
>On Thu, Apr 24, 2003 at 08:17:37AM +0900, Bermejo, Rodrigo wrote:
>  
>
>>  ar.select {|e| e =~ /cat|small/ }
>>
>>
>>  ar.select {|e| e =~ /cat/ or e != /small/ }
>>
>>rubyway?
>>    
>>
>
>The latter is not an RE match:
>
>  
>
>>>"cat" != /z/
>>>      
>>>
>?>
>(i.e. Ruby will give you an error).
>
>I guess you can write:
>
>ar.select {|e| e =~ /cat/ or not e =~ /small/ }
>
>I don't know if this is the Ruby-way or not, but I do think that Ruby's
>RE's and grep are lacking.  There should be a way to express negation in
>a regular expression, and there should be a way to express several
>conditions in grep.  I guess that the complaint over grep really reduces
>to a complaint over REs.
>
>IMHO one should be able to type some sort of equivalent to
>
>  "/cat/ and not /small/".
>
>Just like we have "/cat|small/".
>
>I have found myself wishing for something like that more than once.
>
>I can see that the exact syntax I wrote can't be made to work, but we can
>probably find an alternate RE-like syntax.  Perhaps something like:
>
> /cat|small/  -> true if matches /cat/ or matches /small/
> /cat&small/  -> true if matches /cat/ and matches /small/
> /cat|!small/ -> true if matches /cat/ or does not match /small/
> /cat&!small/ -> true if matches /cat/ and does not match /small/
>
>Just my $0.02
>
>  
>
>>Krishna Dole wrote:
>>
>>    
>>
>>>I'm quite taken with ruby, but recently I ran into trouble using grep. I
>>>have two questions: first, is there a way to call grep with multiple
>>>regexps? For example, if you had
>>>	ar = ["cat", "dog", "smallcat"]
>>>
>>>and you only wanted strings matching  both "small" and "cat", in perl I
>>>think you could do something like
>>>	ar2 = grep(( /cat/ and /small/ ), ar );
>>>
>>>but in ruby it seems like you have to call grep twice
>>>	ar2 = ar.grep(/cat/).grep(/small/)
>>>
>>>      
>>>
>>  ar.select {|e| e =~ /cat|small/ }
>>
>>
>>    
>>
>>>is there a more elegant solution?
>>>
>>>The second question concerns regexps: how do you indicate that you don't
>>>want to match the specified pattern? For example, if I only wanted
>>>      
>>>
>strings
>  
>
>>>containing "cat" but not containing "small". Once again, I think the perl
>>>would look like this:
>>>	ar2 = grep(( /cat/ and !/small/ ), ar );
>>>
>>>
>>>      
>>>
>>    
>>
>>>but '!' doesn't work for me in ruby. So far I haven't found anything
>>>      
>>>
>about
>  
>
>>>this in Pickaxe or on the web.
>>>
>>>thanks,
>>>Krishna
>>>
>>>
>>>
>>>
>>>      
>>>
>>
>>    
>>
>
>--
>Daniel Carrera
>Graduate Teaching Assistant.  Math Dept.
>University of Maryland.  (301) 405-5137
>
>
>
>  
>

-- 
--------------------------------------------------------
Rodrigo Bermejo              | rodrigo.bermejo@ps.ge.com  
IT-Specialist                | 8*879-0644             
--------------------------------------------------------