Initial data commit

Task/Gamma-function/BASIC256/gamma-function.basic

@@ -0,0 +1,29 @@
+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