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# The Great Computer Language Shootout
# http://shootout.alioth.debian.org/
#
# contributed by Gabriele Renzi
class PiDigitSpigot
def initialize()
@z = Transformation.new 1,0,0,1
@x = Transformation.new 0,0,0,0
@inverse = Transformation.new 0,0,0,0
end
def next!
@y = @z.extract(3)
if safe? @y
@z = produce(@y)
@y
else
@z = consume @x.next!()
next!()
end
end
def safe?(digit)
digit == @z.extract(4)
end
def produce(i)
@inverse.qrst(10,-10*i,0,1).compose(@z)
end
def consume(a)
@z.compose(a)
end
end
class Transformation
attr_reader :q, :r, :s, :t
def initialize (q, r, s, t)
@q,@r,@s,@t,@k = q,r,s,t,0
end
def next!()
@q = @k = @k + 1
@r = 4 * @k + 2
@s = 0
@t = 2 * @k + 1
self
end
def extract(j)
(@q * j + @r) / (@s * j + @t)
end
def compose(a)
self.class.new( @q * a.q,
@q * a.r + r * a.t,
@s * a.q + t * a.s,
@s * a.r + t * a.t
)
end
def qrst *args
initialize *args
self
end
end
WIDTH = 10
n = 2_500 # Integer(ARGV[0])
j = 0
digits = PiDigitSpigot.new
while n > 0
if n >= WIDTH
WIDTH.times {print digits.next!}
j += WIDTH
else
n.times {print digits.next!}
(WIDTH-n).times {print " "}
j += n
end
puts "\t:"+j.to_s
n -= WIDTH
end
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