Difficulty writing a sorting method (Chris Pine's Learn to Program)

Ruby
1

Hi all, I’m very, very new to programming and have been working through
Chris P.'s book. The assignment I’m working on is to write a sorting
method without just using .sort or recursion. It should sort a list of
words alphabetically. Here is what I have so far:

#get list of words
puts “Hello, type as many words as you want, with one word per line!”

words = []
already_sorted = []
unsorted = []
while true
word = gets.chomp.capitalize
if word == ‘’
break
end
end

words.push word

#defining the sorting method
words[0] = w
def alpha_sort words
while w < 1
if w < words.all?
already_sorted << w
end
end
while w < words.length
if w < unsorted.all?
already_sorted << w
end
w += 1
end
end
puts(alpha_sort(words))

The problem seems to be in using a variable to represent the array from
the earlier list as part of defining the alpha_sort method? I don’t know
why that would be a problem though. And I’m sure there’s probably a
bunch of other stuff wrong with it that I can’t even see!
Getting the word list works fine, but afterwards this is the error I get
when running it:
“newwordlist.rb:14:in ‘main’: undefined local variable or method ‘w’ for
main:Object (name error)”

Thanks for your suggestions!

2

I’m fairly new to Ruby myself, but not to programming in general.

The error message you’re getting is about this line:

words[0] = w

just before the “def”.

You’re trying to replace the 0th element of the words array with the
value
of the variable “w”, but you haven’t used “w” yet in your program, so it
is
undefined.

You’ll run into some additional problems when you get into your
alpha_sort_words method, but feel free to ask further about those when
you
get there. A couple of things to think about, though:

  1. What does w represent? Is it a word, or the index of a word in the
    words array? Sometimes you compare it with a number, and sometimes with
    words.all? or unsorted.all?. Think about what it really represents and
    try
    to use it consistently.

  2. Array#all? is intended to take a block. I’m not sure if you’ve
    learned
    about those yet, as I’m unfamiliar with the book you’re using. From the
    way you’re using all? I’m not quite sure what you want the code to do,
    but
    if you get stuck later, please ask.

Hope this helps,
Randy

On Fri, Feb 3, 2012 at 2:56 PM, claire pengelly

3

On Fri, Feb 3, 2012 at 11:56 PM, claire pengelly
[email protected] wrote:

Hi all, I’m very, very new to programming and have been working through
Chris P.'s book.

Welcome to Ruby, I hope you enjoy it !

The assignment I’m working on is to write a sorting
method without just using .sort or recursion. It should sort a list of
words alphabetically. Here is what I have so far:

end
end

words.push word

There’s a problem here. You are pushing the word into the array
outside of the while true loop. This means that when you type a word a
press enter, that word is lost. This goes on until you input an empty
line, which triggers the break. Then you push that word in the array,
but as you have checked that word is the empty string. So you should
put the push inside the loop, after checking for the empty string. As
Randy has pointed out, there are probably other problems down the
line, but try to fix this one so you can move forward, and let us know
how you fare.

Good luck !

Jesus.