Printing polynomials

Question

I am taking a class on ruby and our assignment is to take user input and print out a polynomial. Wondering if I can get any feedback to how to improve my code.

class PolynomialElements
 attr_accessor :element, :size
 def printElement
 if size.to_i == 0
 num = "#{@element}"
 elsif size.to_i == 1
 if element.to_i.abs == 1
 num = "x"
 else
 num = "#{@element}x"
 end
 else
 if element.to_i.abs > 1
 num = "#{@element}x^#{@size}"
 elsif element.to_i.abs == 1
 num = "x^#{@size}"
 end
 end
 end
end
askAgain = true
polyArray = Array.new
while askAgain
 puts "How many numbers do you want to enter? "
 numString = gets
 num = numString.to_i
 while num > 0
 puts "Enter a value for the Polynomial "
 value = gets
 polyArray.push(value.chomp)
 num -= 1
 end
 outputArray = Array.new
 sizeOfArray = polyArray.length
 polyArray.each do |x|
 var = PolynomialElements.new
 sizeOfArray -= 1
 var.size = sizeOfArray
 if x.to_i != 0
 var.element = x
 if var.element.to_i > 0
 outputArray.push("+")
 outputArray.push(var.printElement)
 elsif var.element.to_i < 0
 outputArray.push(var.printElement)
 end
 end
 end
 if outputArray[0] == "+"
 outputArray.delete_at(0);
 end
 outputArray.each do |x|
 print x
 end
 puts
 puts "Enter y to enter new number or anything else to quit"
 cont = gets
 if cont.chomp != "y"
 askAgain = false
 else
 polyArray.clear
 end
end

Answer 1

Ruby agreement is to use snake_case to name methods and variables, and not javaCase. While you could say it's a matter of taste, it's so common in Ruby world you would do better to just stick with it. Ruby programmers also tend to push for initializing arrays like this:

polyArray = []

Your PolynomialElements class is not how you use OOP. It has accessor, but what you pass to them aren't parts of its state - those are arguments for printElement. More proper abstraction would be to make it hold an array of coeficients, and iterate over it to form a string.

class Polynomial
 attr_accessors :coeficients # I think this is a proper name for elements (?)
 def initialize coeficients_array = [0] # default value, just in case
 coeficients = coeficients_array
 end
 def to_s
 coefficients.each_with_object("").with_index do |(coef, str), idx|
 # ...
 end
 end
end

Than, you could use it like:

polynomial = Polynomial.new poly_array
puts polynomial.to_s

Notice that you don't need to operate on array of characters - Ruby string allows you to work in the same way, just use append instead of push, and then you just print/puts it instead of printing each character separately.

---

Generally speaking, you barely ever need to keep track of index of iteration manually with Ruby. This:

num = numString.to_i
while num > 0
 puts "Enter a value for the Polynomial "
 value = gets
 polyArray.push(value.chomp)
 num -= 1
end

could be much better written as

num_string.to_i.times do
 # ...
end

---

Ruby way to do (potentially) infinite loop would be:

loop do
 polyArray = []
 # ...
 cont = gets
 break if cont.chomp != "y"
end

This seems more readable, as we directly talk to our loop itself by breaking it, instead of using variable as a "middleman". Also notice how initializing array inside a loop eliminates need for clearing it.

• Jonah: In to_s, rather than create a local variable and mutate it inside the each loop, you can just use reduce or, better yet, each_with_object
• Borsunho: @Jonah I never was a huge fan of each_with_object, but you're probably right.