factors: Remove most panics

Panics are not the best way of handling errors in Go.  I've replaced
panics with default values whenever a sensible one exists.
Factors(0) does not have a sensible default value (as every number is a
factor of zero), so it still panics.

1 files changed, 26 insertions, 4 deletions

diff --git a/factors/factors_test.go b/factors/factors_test.go
index dec651c..a18d30b 100644
--- a/factors/factors_test.go
+++ b/factors/factors_test.go
@@ -68,10 +68,6 @@ var totativeRatioCases = map[uint]float64{
 }
 
 func totativeRatio(n uint) float64 {
-	if n == 0 {
-		panic("0 has no totative ratio!")
-	}
-
 	return float64(Totient(n)) / float64(n)
 }
 
@@ -214,6 +210,8 @@ var (
 	pt = DigitType{0, Opaque}          // 0P - opaque totatives
 )
 var digitMapCases = map[uint][]DigitType{
+	0: []DigitType{},
+	1: []DigitType{zt},
 	2: []DigitType{zt, ot},
 	3: []DigitType{zt, ot, wt},
 	4: []DigitType{zt, ot, ft, wt},
@@ -263,14 +261,38 @@ func TestGetDigitType(t *testing.T) {
 	}
 }
 
+// A few test cases related to radix zero
+func TestGetDigitTypeMisc(t *testing.T) {
+	t.Run("GetDigitType(0, 0)", func(t *testing.T) {
+		if GetDigitType(0, 0) != ft {
+			t.Errorf("GetDigitType(0, 0) = %s, expected 1R", GetDigitType(0, 0))
+		}
+	})
+	t.Run("GetDigitType(1, 0)", func(t *testing.T) {
+		if GetDigitType(1, 0) != ot {
+			t.Errorf("GetDigitType(1, 0) = %s, expected 0R", GetDigitType(1, 0))
+		}
+	})
+	t.Run("GetDigitType(2, 0)", func(t *testing.T) {
+		if GetDigitType(2, 0) != pt {
+			t.Errorf("GetDigitType(2, 0) = %s, expected 0P", GetDigitType(2, 0))
+		}
+	})
+}
+
 var splitCases = map[uintPair]uintPair{
 	// digit, radix, regular part, totative part
 	uintPair{0, 0}:    uintPair{0, 1},
+	uintPair{0, 1}:    uintPair{1, 0},
 	uintPair{0, 2}:    uintPair{1, 0},
 	uintPair{0, 12}:   uintPair{1, 0},
 	uintPair{1, 0}:    uintPair{1, 1},
 	uintPair{20, 0}:   uintPair{1, 20},
 	uintPair{360, 0}:  uintPair{1, 360},
+	uintPair{1, 1}:    uintPair{1, 1},
+	uintPair{12, 1}:   uintPair{1, 12},
+	uintPair{87, 1}:   uintPair{1, 87},
+	uintPair{120, 1}:  uintPair{1, 120},
 	uintPair{1, 2}:    uintPair{1, 1},
 	uintPair{1, 3}:    uintPair{1, 1},
 	uintPair{1, 7}:    uintPair{1, 1},