Doing chris pine learn to program - chapter 7 challenge feedback

Ruby
1

Hi, I’m totally new to ruby and web development (with only
html/css/javascript and some php experience).

I want to get into RoR development but would like to get a good
understanding of ruby before doing railstutorial.org.

I’m following Chris P.'s online tutorial for ruby and just spent a few
hours on this one challenge at chapter 7… you take
input from a user, store it all into an array then have to print it back
out in alphabetical order. But without the sort method.

I purposely didn’t look up any other methods or for help, to see if this
could be accomplished only with what was taught up to that point (no
writing def, or using other methods/loops that weren’t covered)

Here’s the resulting code, it looks messy… but feedback would be
appreciated.

words = []
endProg = nil

while endProg != ‘’
words.push gets.chomp
endProg = words.last
end

words.pop
num1 = -1
num2 = 0
more = 0
value1 = nil
value2 = nil

while more < words.length
words.each do |sort|
if num1 < (words.length - 1)
if value1 != ‘reset’
value2 = value1
value1 = sort
if value2 != nil and value1 != nil and value1 != value2
if value2 > value1
words[num1] = value1
words[num2] = value2
#Here, I skip over the rest of the each loop and do the
#while loop again
#so I don’t over write any of the old values
num1 = num1 + words.length
# reducing the more because we need an extra iteration
more = more - 1
end
end
else
value1 = sort
end
num1 = num1 + 1
num2 = num2 + 1
end
end
words = words
num1 = -1
num2 = 0
sort = nil
value1 = ‘reset’
value2 = ‘reset’
more = more + 1
end

puts
puts words
puts

Obviously this could be done more efficiently with more operators and
methods, but could this have been done better by using only the basics
(do, while, if, else, pop, push, last)

Thanks

2

Hi Mark,

I hope you don’t be angry but I took your question as an exercise for
myself.
I created a repo to log the changes on your code step-by-step.
Take a look at it

I’ll have to stop working on it by now (because it’s work/job time now).
I’ll come back to it at night.

Some things of note that is already commited on the repo.

  1. What happens if the user enters “reset” as one of the words to be
    sorted?
  2. What the “words = words” assignment really do?
  3. To change an Array inside its iteration can be dangerous as you do
    in “words[num1] = value1”

OBS: I couldn’t find the “original” tutorial url. Can you show me?

By the way, congratulations, your code works!
Keep going on Ruby!

Let’s see if somebody else fork the repo and join us in this exercise.

Abinoam Jr.

3

Hi Abinoam,

Thanks for taking the time to look at the code. I have no problems with
you putting it onto github.

the original tutorial is here:
http://pine.fm/LearnToProgram/
and the chapter that contains this challenge I posted about in this
thread:
http://pine.fm/LearnToProgram/?Chapter=07
at the bottom.

  1. In my mind, the words = words should be trying to save the changes
    made to the words array with what was reconstructed during the each
    loop. I wasn’t sure if doing the words[num1] = value1 would
    permanently change the words array, or just change it for the duration
    of the each loop but then when the while loop ran once again, it’d use
    the old words array.

I will take a look at your code, thanks!

4

On Aug 13, 2013, at 9:40 PM, mark ducasi [email protected] wrote:

Hi, I’m totally new to ruby and web development (with only
html/css/javascript and some php experience).

Hi, Mark! Welcome!

I want to get into RoR development but would like to get a good
understanding of ruby before doing railstutorial.org.

This is a good way to do things.

appreciated.
The first question is: does it work? That’s the most important part.

My advice looking at your code is pretty minimal. Given the constraints
you’ve outlined, you’ve done a pretty good job. The one thing I would
strongly recommend is make your variables more clear as to their
purpose. num1, num2, value1, value2 are not actually descriptive,
although marginally better than i,j or n,m as you see in most algorithm
descriptions. Terseness isn’t necessarily a virtue in naming things
(unless it’s hard to type). Also, giving a variable the name ‘sort’ can
end up being problematic for a couple of reasons: (a) it’s a verb,
therefore doesn’t really make sense as a noun (b) there is a well-known
method called sort (which you can’t use) but sometimes a variable name
given the same name as a method can block the method when you want it. A
better name might be ‘sorting_word’ as that’s what it appears to be.

   if value1 != 'reset'
           # reducing the more because we need an extra iteration

words = words
puts

Obviously this could be done more efficiently with more operators and
methods, but could this have been done better by using only the basics
(do, while, if, else, pop, push, last)

I notice you are using .each in there which is a looping mechanism
does this violate your constraint on only using basics?

I haven’t gone through Pine’s tutorial, so I am not sure about this.

To me, one of the biggest issues around learning to program is learning
how to break a problem down into it’s parts. Back in the day we used to
refer to this as Top Down Design (TDD has taken a different meaning
today). But without being able to define methods, it seems like you end
up not actually learning how to implement that. It generally can make
for much more readable and understandable code (as long as it isn’t hard
to find the methods).

Great work so far! Your code looks clean, the operation is clear, you
included some comments of the sort I would find useful.

5

Hi Mark,

Just committed and pushed (my) exercise.
I modified your code step by step in each commit and left comments so
that you can follow the reasoning of each modification.

Your code turned into a pure bubble sort implementation bellow.
Believe me… this is a patch to your initial code! :slight_smile:
It behaves (almost) exactly the same as your initial code.

words = []

words.push gets.chomp while words.last != ‘’

words.pop

begin
more = false
1.upto(words.length-1) do |word_ix|
if words[word_ix-1] > words[word_ix]
words[word_ix-1], words[word_ix] = words[word_ix],
words[word_ix-1]
more = true
end
end
end while more

puts
puts words
puts

It’s pushed to GitHub - abinoam/word_sort: In reply to https://www.ruby-forum.com/topic/4416380

Abinoam Jr.

Hint: (as Rafael said)

6

@Abinoam Jr
Nice, pretty elegant code!

7

I think you should take a look at some methods of sorting and choose
which you think is the best.

I chose bubble because it is the simplest and I came up with this, what
do you think?:

1 class WordList
2 @words
3
4 def initialize
5 @words = []
6 end
7
8 def add word
9 @words.push word
10 end
11
12 def show
13 @words
14 end
15
16 def sort
17 sorted = @words
18 length = sorted.length
19
20 begin
21 swap = false
22
23 sorted.each_index do |e|
24 next_key = e + 1
25
26 next if next_key >= length
27
28 if sorted[e] > sorted[next_key]
29 sorted[e], sorted[next_key] = sorted[next_key], sorted[e]
30 swap = true
31 end
32 end
33 end while swap
34
35 sorted
36 end
37 end
38
39 class Main
40 @words
41
42 def initialize
43 @words = WordList.new
44
45 write_some_words
46 show_words
47 show_sorted
48 end
49
50 def write_some_words
51 msg = “Type something:”
52
53 puts msg
54
55 while((word = gets.chomp) != ‘’) do
56 puts msg
57 @words.add word
58 end
59 end
60
61 def show_words
62 p @words.show
63 end
64
65 def show_sorted
66 p @words.sort
67 end
68 end
69
70 Main.new