28 lines
697 B
Python
28 lines
697 B
Python
from cmath import *
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# Coefficients used by the GNU Scientific Library
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g = 7
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p = [0.99999999999980993, 676.5203681218851, -1259.1392167224028,
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771.32342877765313, -176.61502916214059, 12.507343278686905,
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-0.13857109526572012, 9.9843695780195716e-6, 1.5056327351493116e-7]
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def gamma(z):
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z = complex(z)
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# Reflection formula
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if z.real < 0.5:
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return pi / (sin(pi*z)*gamma(1-z))
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else:
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z -= 1
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x = p[0]
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for i in range(1, g+2):
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x += p[i]/(z+i)
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t = z + g + 0.5
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return sqrt(2*pi) * t**(z+0.5) * exp(-t) * x
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def factorial(n):
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return gamma(n+1)
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print "factorial(-0.5)**2=",factorial(-0.5)**2
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for i in range(10):
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print "factorial(%d)=%s"%(i,factorial(i))
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