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require 'test/unit' | |
# Class for printing the polynomial in string form given the coefficients in an array. | |
# Assumptions: Coefficents are whole numbers only. | |
class Polynomial | |
def initialize (arg) | |
raise ArgumentError, "Need at least 2 coefficients" if arg.size < 2 | |
@coefficients = arg | |
end | |
# Function for printing the polynomial | |
def to_s | |
# create an array of the variable and degrees. For eg, if the number of coefficients is 3, then the array of is ["x^3", "x^2", "x", ""] | |
variable_degree = Array.new(@coefficients.size) {|i| i} | |
variable_degree.reverse!.collect! do|i| | |
if i == 1 | |
"x" | |
elsif i >= 1 | |
"x^#{i}" | |
end | |
end | |
variable_degree.compact! | |
variable_degree << "" | |
# make a sum of the terms of the polynomial using the coefficients and the variable_degree array | |
expr = @coefficients.inject('') do |sum,obj| | |
if obj == 0 | |
variable_degree.shift | |
next sum | |
elsif obj == 1 | |
asd = '+' | |
elsif obj == -1 | |
asd = '-' | |
elsif obj > 1 | |
asd = '+' + obj.to_s | |
else | |
asd = obj.to_s | |
end | |
sum + asd + variable_degree.shift | |
end | |
expr = "0" if expr.eql? "" # If result is "" string then make it "0" | |
expr.sub!(/^\+/,'') # remove the leading '+' sign | |
expr | |
end | |
end | |
# unit tests for testing the Polynomial class | |
class Polynomial_Test < Test::Unit::TestCase | |
def setup | |
@p1 = Polynomial.new([-3,-4,1,0,6]) | |
@p2 = Polynomial.new([1,0,2]) | |
@p3 = Polynomial.new([-1,-2,3,0]) | |
@p4 = Polynomial.new([0,0,0]) | |
end | |
def test_first_negative | |
assert_equal("-3x^4-4x^3+x^2+6", @p1.to_s) | |
end | |
def test_simple | |
assert_equal("x^2+2", @p2.to_s) | |
end | |
def test_first_minus_one | |
assert_equal("-x^3-2x^2+3x", @p3.to_s) | |
end | |
def test_all_zero | |
assert_equal("0", @p4.to_s) | |
end | |
def test_error | |
e = assert_raise(ArgumentError) { Polynomial.new([1]) } | |
assert_match(/Need at least 2 coefficients/, e.message) | |
end | |
def test_misc | |
assert_equal("-x^3+2x^2-3x-4", Polynomial.new([-1,2,-3,-4]).to_s) | |
assert_equal("x^4+3x^2+5", Polynomial.new([0,1,0,3,0,5]).to_s) | |
assert_equal("9x^5", Polynomial.new([9,0,0,0,0,0]).to_s) | |
end | |
end |
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