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class Polynomial
def initialize(arg)
raise ArgumentError.new('We expect an array at least') unless arg.is_a? Array
raise ArgumentError.new('Need at least 2 coefficients') if arg.length < 2
@exponents = []
arg.reverse.inject(0) do |index,item|
@exponents.push( { "factor" => item, "exponent" => index }) unless item == 0
index + 1
end
end
def to_s
return "0=0" if @exponents.length == 0
@exponents.reverse.inject("") do |result, exp|
f = exp["factor"]
e = exp["exponent"]
# show only the '+' when positive and not the first item,
# when negative, the '-' should always be shown
result << "+" if f > 0 && !result.empty?
result << "-" if f < 0
# show the factor only when the absolute value is greater than 1
result << f.abs.to_s if f.abs > 1
# only show the x when the exponent is different from '0'
result << "x" unless e == 0
# only show the exponent when it is not in the range (0..1)
result << "^#{e}" unless (0..1).include?(e)
result
end
end
end
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