38 lines
819 B
Plaintext
38 lines
819 B
Plaintext
func gamma(z) {
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var epsilon = 0.0000001
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func withinepsilon(x) {
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abs(x - abs(x)) <= epsilon
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}
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var p = [
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676.5203681218851, -1259.1392167224028,
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771.32342877765313, -176.61502916214059,
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12.507343278686905, -0.13857109526572012,
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9.9843695780195716e-6, 1.5056327351493116e-7,
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]
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var result = 0
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const pi = Num.pi
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if (z.re < 0.5) {
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result = (pi / (sin(pi * z) * gamma(1 - z)))
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}
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else {
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z -= 1
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var x = 0.99999999999980993
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p.each_kv { |i, v|
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x += v/(z + i + 1)
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}
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var t = (z + p.len - 0.5)
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result = (sqrt(pi*2) * t**(z+0.5) * exp(-t) * x)
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}
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withinepsilon(result.im) ? result.re : result
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}
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for i in 1..10 {
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say ("%.14e" % gamma(i/3))
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}
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