[ruby-talk:11367] Palindromes, $/, chomp, and lesser surprises.

I have written my first Ruby program, a translation of a Perl program
I had written to find all of the palindromes in a word list.

   def make_regex(length)
     re = '^'
     re += '(.)' * (length / 2)
     re += '.' if length % 2 > 0
     (length/2).downto(1) {|i| re += "\\#{i}" }
     re += '$'
     Regexp.new(re, 'i')
   end

   recache = []
   while gets
     chop!
     length = $_.length
     recache[length] ||= make_regex(length)
     print $_, "\n" if recache[length] =~ $_
   end

I had originally tried to use chomp! rather than chop!, as my Perl
background led me to expect that $/ would be set in a
platform-appropriate way (i.e., "\r\n" on my Win32 box), and that
chomp! would therefore strip $_ as I expected.  If I were explicitly
to set $/, my script would break on a platform that uses "\n" to
separate lines.

Reading about the chop/chomp family at our Pragmatic friends' site led
me to understand the special behavior of chop; now the program works
just fine (and runs a good deal faster than the Perl equivalent, for
what it's worth).

Now, if chomp means "safely deal with end-of-line cruft", and chop
means "remove the last character, period", then one could argue that
to have chop handle the special case of Win32-esque line endings
violates the principle of least surprise.  Any comments?

Also, I'm curious as to which idiom is more Rubyish: "while gets" or
"ARGF.each { |line| #block }".  Do the two have different
implications?

-- 
Jonathan Feinberg   [e-mail]   Sunny Brooklyn, NY
http://pobox.com/~jdf