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polynomial.rb
Ruby
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class Polynomial
def initialize(coefficients)
@coefficients = coefficients.reverse # reverse so the index equates to the exponent of each coefficient
raise ArgumentError, 'Need at least 2 coefficients' if coefficients.size < 2
end
def to_s
# Build an array of sprintfs, LIFO to get most significant order
@coefficients.inject([]) {|builder, coefficient| ["%+ix^%i" % [coefficient, builder.size]] + builder}.to_s.
gsub(/(\+0x\^\d+|x\^0|\^1\d{0})/, ''). # Clean out 0x^y, x^0, ^1
gsub(/\d{0}1x/, 'x'). # Replace 1x with just x
sub(/^\+/, ''). # Remove leading +
sub(/^$/, '0') # 0 when blank
end
end
polynomial_test.rb
Ruby
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require 'test/unit'
require 'test/unit/ui/console/testrunner'
require 'polynomial'
 
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])
@p5 = Polynomial.new([6,5,4,3,2,1])
@p6 = Polynomial.new([0,5,4,3,2,1])
@p7 = Polynomial.new([1,0])
@p8 = Polynomial.new([1,0,0])
@p9 = Polynomial.new([1,1,1,1,0])
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_last_is_one
assert_equal("6x^5+5x^4+4x^3+3x^2+2x+1", @p5.to_s)
end
def test_zero_up_front
assert_equal("5x^4+4x^3+3x^2+2x+1", @p6.to_s)
end
def test_lots_of_ones
assert_equal("x^4+x^3+x^2+x", @p9.to_s)
end
def test_short
assert_equal("x", @p7.to_s)
end
 
def test_all_zero
assert_equal("0", @p4.to_s)
end
def test_last_two_zero
assert_equal("x^2", @p8.to_s)
end
 
def test_error
e = assert_raise(ArgumentError) { Polynomial.new([1]) }
assert_match(/Need at least 2 coefficients/, e.message)
end
end
 
Test::Unit::UI::Console::TestRunner.run(Polynomial_Test)

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