I'm trying to teach myself Ruby via coding Conway's Game of Life.
One of my preliminary steps to learn how arrays work is to create an array of arrays of Cell objects defined as follows:
class Cell
def initialize(status, xpos, ypos)
#status = status
#position = [xpos,ypos]
end
end
contents = Array.new(10, Array.new(10))
for i in 0..contents.length-1
for j in 0..9
contents.at(i).insert(j, Cell.new("DEAD", i, j))
end
end
I would expect that <code>contents</code> would be a size 10 array (which it is) where each of the inner arrays are also of size 10; however each of the inner arrays end up being size 110, why is that?
EDIT
So it seems my main issue was misunderstanding how insert works. I've since changed my code to as follows:
class Cell
def initialize(status, xpos, ypos)
#status = status
#position = [xpos,ypos]
end
def declare_state
puts "Position is [" + #position[0].to_s + ", " + #position[1].to_s + "] and status is " + #status
end
end
contents = Array.new(10, Array.new(10))
for i in 0..9
for j in 0..9
contents[i][j] = Cell.new("DEAD", i, j))
end
end
contents.each {
|subarray| subarray.each {
|cell| cell.declare_status
}
}
It looks like all the #xpos values for all my Cell objects is being set to 9, which is unexpected.
I know this doesn't directly relate, but one way to fix this that would be more idiomatic with ruby would be to use each_with_index instead of having nested for loops. It would look like this:
class Cell
def initialize(status, xpos, ypos)
#status = status
#position = [xpos,ypos]
end
end
contents = Array.new(10, Array.new(10))
contents.each_with_index do |row, row_index|
row.each_with_index do |cell, cell_index|
contents[row_index][cell_index] = Cell.new("DEAD", row_index, cell_index)
end
end
In the line:
contents = Array.new(10, Array.new(10))
an array with 10 positions is created. What you may not realize is that each of those positions is filled with the same array.
I think you wanted
contents = Array.new(10) { Array.new(10) }
There are two issues here. First is your use of insert, which is creating new elements in the sub-arrays rather than editing the values. Rather than contents.at(i).insert(j, cell) you could use contents[i][j] = cell where cell is your cell object.
The second issue is that your use of contents = Array.new(10, Array.new(10)) is creating one array with 10 elements referring to the same single array reference. If you run the object_id to each sub-array, you will see they all refer to the same object. Updating one of the sub-arrays will appear to update all of them as a result.
I have built a version of mastermind that checks a user's input and provides feedback based on how close the user's guess was to the winning sequence. If you're not familiar with the game, you get feedback indicating how many of your characters were guessed correctly at the same index and how many characters guessed are in the sequence, but at the wrong index. If there are duplicates in the guess, then you would not count the extra values unless they correspond to the same number of duplicates in the secret code.
Example: If the sequence is ["G","G","G","Y"] and the user guesses ["G", "Y","G","G"] then you'd want to return 2 for items at the same index and 2 for items at different indexes that are included in the secret sequence.
Another example: If the sequence is ["X","R","Y","T"] and the user guesses ["T","T","Y","Y"] then you'd return 1 for items at the same index 1 for the character guessed that is in the sequence but at the wrong index.
Anyway, to me this is not a simple problem to solve. Here's the code I used to get it to work, but it's not elegant. There must be a better way. I was hoping someone can tell me what I'm missing here?? New to Ruby...
def index_checker(input_array, sequence_array)
count = 0
leftover_input = []
leftover_sequence = []
input.each_with_index do |char, idx|
if char == sequence[idx]
count += 1
else
leftover_input << char
leftover_sequence << sequence[idx]
end
end
diff_index_checker(leftover_input, leftover_sequence, count)
end
def diff_index_checker(input, sequence, count)
count2 = 0
already_counted = []
input.each do |char|
if sequence.include?(char) && !already_counted.include?(char)
count2 += 1
already_counted << char
end
end
[count, count2]
end
Here's a clean Ruby solution, written in idiomatic Ruby object-oriented style:
class Mastermind
def initialize(input_array, sequence_array)
#input_array = input_array
#sequence_array = sequence_array
end
def matches
[index_matches, other_matches]
end
def results
[index_matches.size, other_matches.size]
end
private
attr_reader :input_array, :sequence_array
def index_matches
input_array.select.with_index { |e, i| e == sequence_array[i] }
end
def other_matches
non_exact_input & non_exact_sequence
end
def non_exact_input
array_difference(input_array, index_matches)
end
def non_exact_sequence
array_difference(sequence_array, index_matches)
end
# This method is based on https://stackoverflow.com/a/3852809/5961578
def array_difference(array_1, array_2)
counts = array_2.inject(Hash.new(0)) { |h, v| h[v] += 1; h }
array_1.reject { |e| counts[e] -= 1 unless counts[e].zero? }
end
end
You would use this class as follows:
>> input_array = ["G","G","G","Y"]
>> sequence_array = ["G", "Y","G","G"]
>> guess = Mastermind.new(input_array, sequence_array)
>> guess.results
#> [2, 2]
>> guess.matches
#> [["G", "G"], ["G", "Y"]]
Here's how it works. First everything goes into a class called Mastermind. We create a constructor for the class (which in Ruby is a method called initialize) and we have it accept two arguments: input array (the user guess), and sequence array (the answer).
We set each of these arguments to an instance variable, which is indicated by its beginning with #. Then we use attr_reader to create getter methods for #input_array and #sequence_array, which allows us to get the values by calling input_array and sequence_array from any instance method within the class.
We then define two public methods: matches (which returns an array of exact matches and an array of other matches (the ones that match but at the wrong index), and results (which returns a count of each of these two arrays).
Now, within the private portion of our class, we can define the guts of the logic. Each method has a specific job, and each is named to (hopefully) help a reader understand what it is doing.
index_matches returns a subset of the input_array whose elements match the sequence_array exactly.
other_matches returns a subset of the input_array whose elements do not match the sequence_array exactly, but do match at the wrong index.
other_matches relies on non_exact_input and non_exact_sequence, each of which is computed using the array_difference method, which I copied from another SO answer. (There is no convenient Ruby method that allows us to subtract one array from another without deleting duplicates).
Code
def matches(hidden, guess)
indices_wo_match = hidden.each_index.reject { |i| hidden[i] == guess[i] }
hidden_counts = counting_hash(hidden.values_at *indices_wo_match)
guess_counts = counting_hash(guess.values_at *indices_wo_match)
[hidden.size - indices_wo_match.size, guess_counts.reduce(0) { |tot, (k, cnt)|
tot + [hidden_counts[k], cnt].min }]
end
def counting_hash(arr)
arr.each_with_object(Hash.new(0)) { |s, h| h[s] += 1 }
end
Examples
matches ["G","G","G","Y"], ["G", "Y","G","G"]
#=> [2, 2]
matches ["X","R","Y","T"] , ["T","T","Y","Y"]
#=> [1, 1]
Explanation
The steps are as follows.
hidden = ["G","G","G","Y"]
guess = ["G", "Y","G","G"]
Save the indices i for which hidden[i] != guess[i].
indices_wo_match = hidden.each_index.reject { |i| hidden[i] == guess[i] }
#=> [1, 3]
Note that the number of indices for which the values are equal is as follows.
hidden.size - indices_wo_match.size
#=> 2
Now compute the numbers of remaining elements of guess that pair with one of the remaining values of hidden by having the same value. Begin by counting the numbers of instances of each unique element of hidden and then do the same for guess.
hidden_counts = counting_hash(hidden.values_at *indices_wo_match)
#=> {"G"=>1, "Y"=>1}
guess_counts = counting_hash(guess.values_at *indices_wo_match)
#=> {"Y"=>1, "G"=>1}
To understand how counting_hash works, see Hash::new, especially the explanation of the effect of providing a default value as an argument of new. In brief, if a hash is defined h = Hash.new(3), then if h does not have a key k, h[k] returns the default value, here 3 (the hash is not changed).
Now compute the numbers of matches of elements of guess that were not equal to the value of hidden at the same index and which pair with an element of hidden that have the same value.
val_matches = guess_counts.reduce(0) do |tot, (k, cnt)|
tot + [hidden_counts[k], cnt].min
end
#=> 2
Lastly, return the values of interest.
[hidden.size - indices_wo_match.size, val_matches]
#=> [2, 2]
In the code presented above I have substituted out the variable val_matches.
With Ruby 2.4+ one can use Enumerable#sum to replace
guess_counts.reduce(0) { |tot, (k, cnt)| tot + [hidden_counts[k], cnt].min }
with
guess_counts.sum { |k, cnt| [hidden_counts[k], cnt].min }
def judge(secret, guess)
full = secret.zip(guess).count { |s, g| s == g }
semi = secret.uniq.sum { |s| [secret.count(s), guess.count(s)].min } - full
[full, semi]
end
Demo:
> judge(["G","G","G","Y"], ["G","Y","G","G"])
=> [2, 2]
> judge(["X","R","Y","T"], ["T","T","Y","Y"])
=> [1, 1]
A shorter alternative, though I find it less clear:
full = secret.zip(guess).count(&:uniq!)
I prefer my other answer for its simplicity, but this one would be faster if someone wanted to use this for arrays larger than Mastermind's.
def judge(secret, guess)
full = secret.zip(guess).count { |s, g| s == g }
pool = secret.group_by(&:itself)
[full, guess.count { |g| pool[g]&.pop } - full]
end
Demo:
> judge(["G","G","G","Y"], ["G","Y","G","G"])
=> [2, 2]
> judge(["X","R","Y","T"], ["T","T","Y","Y"])
=> [1, 1]
I have a long code but I tried to copy and adapt my problem in as few lines as possible . I have a method which creates an array( 2D ) with 0 and 1
array1 = newValue(2) - the number 2 represents how many 1 the array has
array2 = newValue(3)
and this loop
(0..9).each do|i|
(0..9).each do|j|
while((array1[i][j] == array2[i][j]) && (array2[i][j] == 1)) do
array1 = newvalue(2)
array2 = newvalue(3)
end
end
end
I'm using the while loop so I won t have a 1 in the same position in both arrays . But what is inside the while loop doesn't modify the values of the array . I also tried using map!/collect! but I think I did something wrong because nothing happened. I hope you can understand what I was trying to do .
Edit:
def newValue(value)
value = value.to_i
array = Array.new(10) { Array.new(10 , 0) }
(a lot of conditions on how to position the items in the array)
return array
end
Here's my take... hopefully it'll help out. It seems that what you noticed was true. The arrays are not getting reset. Probably because inside the each blocks, the scope is lost. This is probably because the are arrays. I took a slightly different approach. Put everything in a class so you can have instance variables that you can control and you know where they are and that they are always the same.
I pulled out the compare_arrays function which just returns the coordinates of the match if there is one. If not it returns nil. Then, youre while loop is simplified in the reprocess method. If you found a match, reprocess until you don't have a match any more. I used a dummy newValue method that just returned another 2d array (as you suggested yours does). This seems to do the trick from what I can tell. Give it a whirl and see what you think. You can access the two arrays after all the processing with processor.array1 as you can see I did at the bottom.
# generate a random 2d array with 0's and val's
def generateRandomArray(val=1)
array = []
(0..9).each do |i|
(0..9).each do |j|
array[i] ||= []
array[i][j] = (rand > 0.1) ? 0 : val
end
end
array
end
array1 = generateRandomArray
array2 = generateRandomArray
def newValue(val)
generateRandomArray(val)
end
class Processor
attr_reader :array1, :array2
def initialize(array1, array2)
#array1 = array1
#array2 = array2
end
def compare_arrays
found = false
for ii in 0..9
break unless for jj in 0..9
if ((#array2[ii][jj] == 1) && (#array1[ii][jj] == 1))
found = true
break
end
end
end
[ii,jj] if found
end
def reprocess
while compare_arrays
puts "Reprocessing"
#array1 = newValue(2)
#array2 = newValue(3)
reprocess
end
end
end
processor = Processor.new(array1, array2)
processor.reprocess
puts processor.array1.inspect
I'm trying to find the inverse document frequency for a categorization algorithm and am having trouble getting it the way that my code is structured (with nested hashes), and generally comparing one hash to many hashes.
My training code looks like this so far:
def train!
#data = {}
#all_books.each do |category, books|
#data[category] = {
words: 0,
books: 0,
freq: Hash.new(0)
}
books.each do |filename, tokens|
#data[category][:words] += tokens.count
#data[category][:books] += 1
tokens.each do |token|
#data[category][:freq][token] += 1
end
end
#data[category][:freq].map { |k, v| v = (v / #data[category][:freq].values.max) }
end
end
Basically, I have a hash with 4 categories (subject to change), and for each have word count, book count, and a frequency hash which shows term frequency for the category. How do I get the frequency of individual words from one category compared against the frequency of the words shown in all categories? I know how to do the comparison for one set of hash keys against another, but am not sure how to loop through a nested hash to get the frequency of terms against all other terms, if that makes sense.
Edit to include predicted outcome -
I'd like to return a hash of nested hashes (one for each category) that shows the word as the key, and the number of other categories in which it appears as the value. i.e. {:category1 = {:word => 3, :other => 2, :third => 1}, :category2 => {:another => 1, ...}} Alternately an array of category names as the value, instead of the number of categories, would also work.
I've tried creating a new hash as follows, but it's turning up empty:
def train!
#data = {}
#all_words = Hash.new([]) #new hash for all words, default value is empty array
#all_books.each do |category, books|
#data[category] = {
words: 0,
books: 0,
freq: Hash.new(0)
}
books.each do |filename, tokens|
#data[category][:words] += tokens.count
#data[category][:books] += 1
tokens.each do |token|
#data[category][:freq][token] += 1
#all_words[token] << category #should insert category name if the word appears, right?
end
end
#data[category][:freq].map { |k, v| v = (v / #data[category][:freq].values.max) }
end
end
If someone can help me figure out why the #all_words hash is empty when the code is run, I may be able to get the rest.
I haven't gone through it all, but you certainly have an error:
#all_words[token] << category #should insert category name if the word appears, right?
Nope. #all_words[token] will return empty array, but not create a new slot with an empty array, like you're assuming. So that statement doesn't modify the #all_words hash at all.
Try these 2 changes and see if it helps:
#all_words = {} # ditch the default value
...
(#all_words[token] ||= []) << category # lazy-init the array, and append
Excuse the newbie question. I'm trying to create a two dimensional array in ruby, and initialise all its values to 1. My code is creating the two dimensional array just fine, but fails to modify any of its values.
Can anyone explain what I'm doing wrong?
def mda(width,height)
#make a two dimensional array
a = Array.new(width)
a.map! { Array.new(height) }
#init all its values to 1
a.each do |row|
row.each do |column|
column = 1
end
end
return a
end
It the line row.each do |column| the variable column is the copy of the value in row. You can't edit its value in such way. You must do:
def mda(width,height)
a = Array.new(width)
a.map! { Array.new(height) }
a.each do |row|
row.map!{1}
end
return a
end
Or better:
def mda(width,height)
a = Array.new(width)
a.map! { Array.new(height) }
a.map do |row|
row.map!{1}
end
end
Or better:
def mda(width,height)
a = Array.new(width){ Array.new(height) }
a.map do |row|
row.map!{1}
end
end
Or better:
def mda(width,height)
Array.new(width) { Array.new(height){1} }
end
each passes into the block parameter the value of each element, not the element itself, so column = 1 doesn't actually modify the array.
You can do this in one step, though - see the API docs for details on the various forms of Array#new. Try a = Array.new(width) {|i| Array.new(height) {|j| 1 } }
you can create it like this?
a=Array.new(width) { Array.new(height,1) }
column in your nested each loop is a copy of the value at that place in the array, not a pointer/reference to it, so when you change its value you're only changing the value of the copy (which ceases to exist outside the block).
If you just want a two-dimensional array populated with 1s something as simple as this will work:
def mda(width,height)
[ [1] * width ] * height
end
Pretty simple.
By the way, if you want to know how to modify the elements of a two-dimensional array as you're iterating over it, here's one way (starting from line 6 in your code):
#init all its values to 1
a.length.times do |i|
a[i].length.times do |j|
a[i][j] = 1
end
end