Gamma function: Difference between revisions

=={{header|BASIC256}}==

{{trans|FreeBASIC}} - Stirling method.

{{trans|Phix}} - Lanczos method.

<lang freebasic>print " x Stirling Lanczos"

print

for i = 1 to 20

d = i / 10.0

print d;

print chr(9); ljust(string(gammaStirling(d)), 13, "0");

print chr(9); ljust(string(gammaLanczos(d)), 13, "0")

next i

end

function gammaStirling (x)

e = exp(1) # e is not predefined in BASIC256

return sqr(2.0 * pi / x) * ((x / e) ^ x)

end function

function gammaLanczos (x)

dim p = {0.99999999999980993, 676.5203681218851, -1259.1392167224028, 771.32342877765313, -176.61502916214059, 12.507343278686905, -0.13857109526572012, 9.9843695780195716e-6, 1.5056327351493116e-7}

g = 7

if x < 0.5 then return pi / (sin(pi * x) * gammaLanczos(1-x))

x -= 1

a = p[0]

t = x + g + 0.5

for i = 1 to 8

a += p[i] / (x + i)

next i

return sqr(2.0 * pi) * (t ^ (x + 0.5)) * exp(-t) * a

end function</lang>