Hi,
I am a beginner in ruby and It try to undertand the concept of
"enum.chunk" in particular these 2 exemples (http://ruby-doc.org/core/
classes/Enumerable.html#M003131)
" open("/usr/share/dict/words", "r:iso-8859-1") {|f|
f.chunk {|line| line.ord }.each {|ch, lines| p [ch.chr,
lines.length] } "
and
" sep = "-"*72 + "\n"
IO.popen("svn log README") {|f|
f.chunk {|line|
line != sep || nil
}.each {|_, lines|
pp lines
}
}
"
What do those mean ? I can''t understand the way it works...
Best regards,
Jr
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On Sep 12, 10:18 am, Jean-René Saint-Etienne <jeanrene97...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> Hi, > > I am a beginner in ruby and It try to undertand the concept of > "enum.chunk" in particular these 2 exemples (http://ruby-doc.org/core/ > classes/Enumerable.html#M003131) >it groups consecutive elements according to the value of the block you supply, and returns an array of arrays, one for each group> " open("/usr/share/dict/words", "r:iso-8859-1") {|f| > f.chunk {|line| line.ord }.each {|ch, lines| p [ch.chr, > lines.length] } " >this opens a dictionary file, and then groups by the first character of each line, before outputting the size of each group (i.e. the number of words in the dictionary file beginning with that letter) Fred> and > " sep = "-"*72 + "\n" > IO.popen("svn log README") {|f| > f.chunk {|line| > line != sep || nil > }.each {|_, lines| > pp lines > } > } > " > > What do those mean ? I can''t understand the way it works... > > Best regards, > > Jr-- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
result = [2, 4, 1, 3, 5, 6, 8].chunk do |num| num.even? end result.each do |even_result, a_chunk| p [even_result, a_chunk] end --output:-- [true, [2, 4]] [false, [1, 3, 5]] [true, [6, 8]] === e = DATA.chunk do |line| ascii_code_for_first_letter = line.ord end e.each do |ascii_code, lines| character = ascii_code.chr number_of_lines_in_array = lines.length p [character, number_of_lines_in_array] end __END__ a ant apple ball basket cake aztec --output:-- ["a", 3] ["b", 2] ["c", 1] ["a", 1] Note that a dictionary file would not have that last line--all the ''a'' words would be grouped together. As for your last example, the chunk() docs say this: ===The following key values has special meaning: nil .... specifies that the elements are dropped. == If you look at the first example in my post, the elements that fail the test are chunked into a separate group. However, the test in the log file example is written like this: line != sep || nil which is equivalent to: (line != sep) || nil If the line in the file is a bunch of dashes, the the test on the left fails because line is equal to sep. Next, in an or statement: something || something if the left side is true, then ruby doesn''t even execute the right side--because an OR is true if either side of the OR is true. No matter what the right side evaluates to, the OR will be true if the left side is true, so ruby skips the right side if the left side evaluates to true. ruby then returns the value of the left side. So if the line in the file equals a bunch of dashes, then the left side test fails, and so the right side is evaluated and returned. Terrible docs, I would say. -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.