June 2018 Update

Task/Factorial/Go/factorial-3.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+    "fmt"
+    "math"
+)
+
+func factorial(n float64) float64 {
+    return math.Gamma(n + 1)
+}
+
+func main() {
+    for i := 0.; i <= 10; i++ {
+        fmt.Println(i, factorial(i))
+    }
+    fmt.Println(100, factorial(100))
+}

Task/Factorial/Go/factorial-4.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+    "fmt"
+    "math"
+    "math/big"
+)
+
+func lfactorial(n float64) float64 {
+    l, _ := math.Lgamma(n + 1)
+    return l
+}
+
+func factorial(n float64) *big.Float {
+    i, frac := math.Modf(lfactorial(n) * math.Log2E)
+    z := big.NewFloat(math.Exp2(frac))
+    return z.SetMantExp(z, int(i))
+}
+
+func main() {
+    for i := 0.; i <= 10; i++ {
+        fmt.Println(i, factorial(i))
+    }
+    fmt.Println(100, factorial(100))
+    fmt.Println(800, factorial(800))
+}