update

Task/Gamma-function/00DESCRIPTION

@@ -1,4 +1,3 @@
-{{omit from|GAP}}
 Implement one algorithm (or more) to compute the [[wp:Gamma function|Gamma]] (<math>\Gamma</math>) function (in the real field only). If your language has the function as builtin or you know a library which has it, compare your implementation's results with the results of the builtin/library function.
 The Gamma function can be defined as:
 

Task/Gamma-function/Racket/gamma-function.rkt

@@ -0,0 +1,29 @@
+#lang racket
+(define (gamma number)
+  (if (> 1/2 number)
+      (/ pi (* (sin (* pi number))
+               (gamma (- 1.0 number))))
+      (let ((n (sub1 number))
+            (c '(0.99999999999980993 676.5203681218851 -1259.1392167224028
+                 771.32342877765313 -176.61502916214059 12.507343278686905
+	             -0.13857109526572012 9.9843695780195716e-6 1.5056327351493116e-7)))
+        (* (sqrt (* pi 2))
+           (expt (+ n 7 0.5) (+ n 0.5))
+           (exp (- (+ n 7 0.5)))
+           (+ (car c)
+              (apply +
+                (for/list ((i (in-range (length (cdr c)))) (x (in-list (cdr c))))
+                  (/ x (+ 1 n i)))))))))
+
+(map gamma '(0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0))
+;->
+;'(9.513507698668736
+;  4.590843711998802
+;  2.9915689876875904
+;  2.218159543757687
+;  1.7724538509055159
+;  1.489192248812818
+;  1.2980553326475577
+;  1.1642297137253037
+;  1.068628702119319
+;  1.0)