Add totative ratio and factor score to program

1 files changed, 17 insertions, 0 deletions

diff --git a/factors/totative.go b/factors/totative.go
new file mode 100644
index 0000000..558f0f0
--- /dev/null
+++ b/factors/totative.go
@@ -0,0 +1,17 @@
+package factors
+
+// TotativeRatio calculates the fraction of numbers less than n that
+// are totatives of n (share no factors with n)
+func TotativeRatio(n uint) float64 {
+	if n == 0 {
+		panic("0 has no totative ratio!")
+	}
+
+	primeFactorization := PrimeFactorize(n)
+
+	totativeRatio := 1.0
+	for p := range primeFactorization.exponents {
+		totativeRatio *= float64(p - 1) / float64(p)
+	}
+	return totativeRatio
+}