+++++ page 49 Reopening Classes
While ...
the most unique features of Ruby’s class structure: The ability to ...
-----> ^
In French I wouldn’t put a capital letter after a colon.
(Note : I have to use code block instead of quote to keep the arrow and caret aligned with the typo. )
+++++ page 54, paragraph 7 (counting the diagram for one)
You can also index arrays with a pair of numbers, [_start_, _count_]. This returns a new array
consisting of references to count number of objects starting at position start:
-----> should be _count_ number ... at position _start_:
(To be coherent _start_, and _count_ should be used both in the square brackets and in the next line.)
+++++ page 55, paragraph 5, line 2 :
replaced by cat. In the next line, the subarray [2, 0] is of length 0, so dog just is inserted at
-----> dog just is sounds strange to me, I would expect : so dog is just inserted at
+++++ page 55, paragraph 6, line 1 : superfluous what
It’s common to create arrays of short words, but that can be a pain, what with all the quotes
-----> ^^^^ <----- seems superfluous
SUGGESTION
+++++ pages 58-59 : why ’ in the regexp ?
page 58 bottom : the method words_from_string returns : string.downcase.scan(/[\w']+/)
Why an apostrophe in the regexp ([\w']) if the sentence does not contain any (p.59, par.3) :
p words_from_string(“I like Ruby, it is (usually) optimized for programmer happiness”)
In the previous edition (2010), it was :
p words_from_string(“But I didn’t inhale, he said (emphatically)”)
-----> So you could either remove the apostrophe from the regexp (stop ! it breaks the test assert_equal(["the", "cat's", "mat"] ...), or introduce one in the text, for example :
p words_from_string(“I like Ruby, it is (usually) optimized for programmer happiness, isn’t it ? <—”)
and
raw_text = "The problem breaks down into two parts. First, given some text
as a string, return a list of words. That sounds like an array, isn’t it ? <-----
+++++ page 62 : Blocks and Enumeration
In our program that wrote out the results of our word frequency analysis, we had the following loop:
top_five.each do |I|
^^word = top_five[i][0]
^^count = top_five[i][1]
^^puts “#{word}: #{count}”
end
(carets added for indentation)
-----> But this code exists nowhere in this new version. It is a remnant of old versions, for example :
programming-ruby-1-9_p4_.pdf
ISBN-10: 1-934356-08-5
ISBN-13: 978-1-934356-08-1
4.0 printing, May 2011
Version: 2011-5-11
→ second halh of the page 68 :
Download tut_containers/word_freq/ugly_word_count.rb
require_relative "words_from_string.rb"
require_relative "count_frequency.rb"
raw_text = %{
The problem breaks down into two parts. First, given some text as a
string, return a list of words. That sounds like an array. Then, build a
count for each distinct word. That sounds like a use for a hash---we can
index it with the word and use the corresponding entry to keep a count.}
word_list = words_from_string(raw_text)
counts = count_frequency(word_list)
sorted = counts.sort_by {|word, count| count}
top_five = sorted.last(5)
for i in 0...5 # (this is ugly code--read on
word = top_five[i][0] # for a better version)
count = top_five[i][1]
puts "#{word}: #{count}"
end
-----> caution, page 63, line 4 :
A Ruby programmer might use a different enumerator method called map to write this code more compactly.
this code is not in sync with the old for loop.
=====> I have a solution :
in tut_containers/word_freq/better_word_count.rb on page 62 replace :
top_five.reverse_each do |word, count|
by :
top_five.reverse.each do |word, count|
The result is the same. Then : (carets before puts added for indentation)
Blocks and Enumeration
In our program that wrote out the results of our word frequency analysis, we had the following loop:
top_five.reverse.each do |word, count|
^^puts “#{word}: #{count}”
end
→ Then the replacement of each by map on page 63 perfectly corresponds to
puts top_five.reverse.map { |word, count| "#{word}: #{count}" }
in /best_word_count.rb, and that’s it.
+++++ page 63, paragraph after /best_word_count.rb : it ?, of of
The map method is now taking each element of our top five array and converting it to a new
-----> ^^ <----them ???
-----> I would replace it by them (the map method is taking … and converting them (the elements)), or put a comma after top five array :
The map method is now taking each element of our top five array, and converting it [the array] …
-----> + next line (twice of) :
array made of of the strings that come as the result of executing the block.
-----> ^^^^^
+++++ page 64, paragraph 3. I had difficulty to understand this sentence :
All tap does is …, and then return the original receiver of the method (which, from the perspective of the method pipeline does nothing
-----> it would help to add tap :
[line continued] —the receiver
calls the method tap and then the same object is returned ...
-----> ^^^