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3 tristanc 1 
-- function closures are powerful
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-- traditional fixed-point operator from functional programming
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Y = function (g)
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      local a = function (f) return f(f) end
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      return a(function (f)
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                 return g(function (x)
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                             local c=f(f)
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                             return c(x)
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                           end)
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               end)
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end
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-- factorial without recursion
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F = function (f)
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      return function (n)
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               if n == 0 then return 1
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               else return n*f(n-1) end
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             end
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    end
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factorial = Y(F)   -- factorial is the fixed point of F
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-- now test it
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function test(x)
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	io.write(x,"! = ",factorial(x),"\n")
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end
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for n=0,16 do
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	test(n)
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end