cleaned up code

romannumeral.go

@@ -10,46 +10,41 @@ import (
 	"errors"
 )
 
-const (
-	_maxRoman = 3999
-	_minRoman = 1
-)
-
-var (
-	InvalidRomanNumeral = errors.New("invalid roman numeral")
-	IntegerOutOfBounds  = errors.New("integer must be between 1 and 3999")
-)
-
 // numeral describes the value and symbol of a single roman numeral
 type numeral struct {
 	val int
 	sym []byte
 }
 
-// _numerals are all unique numerals ordered from largest to smallest
-var _numerals = []numeral{
-	{1000, []byte("M")},
-	{900, []byte("CM")},
-	{500, []byte("D")},
-	{400, []byte("CD")},
-	{100, []byte("C")},
-	{90, []byte("XC")},
-	{50, []byte("L")},
-	{40, []byte("XL")},
-	{10, []byte("X")},
-	{9, []byte("IX")},
-	{5, []byte("V")},
-	{4, []byte("IV")},
-	{1, []byte("I")},
-}
-
-// lookup arrays used for converting from an int to a roman numeral extremely quickly.
-// method from here: https://rosettacode.org/wiki/Roman_numerals/Encode#Go
 var (
-	m0 = []string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"}
+	// InvalidRomanNumeral - error for when a roman numeral string provided is not a valid roman numeral
-	m1 = []string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"}
+	InvalidRomanNumeral = errors.New("invalid roman numeral")
-	m2 = []string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"}
+	// IntegerOutOfBounds - error for when the integer provided is invalid and unable to be converted to a roman numeral
-	m3 = []string{"", "M", "MM", "MMM"}
+	IntegerOutOfBounds = errors.New("integer must be between 1 and 3999")
+
+	// all unique numerals ordered from largest to smallest
+	nums = []numeral{
+		{1000, []byte("M")},
+		{900, []byte("CM")},
+		{500, []byte("D")},
+		{400, []byte("CD")},
+		{100, []byte("C")},
+		{90, []byte("XC")},
+		{50, []byte("L")},
+		{40, []byte("XL")},
+		{10, []byte("X")},
+		{9, []byte("IX")},
+		{5, []byte("V")},
+		{4, []byte("IV")},
+		{1, []byte("I")},
+	}
+
+	// lookup arrays used for converting from an int to a roman numeral extremely quickly.
+	// method from here: https://rosettacode.org/wiki/Roman_numerals/Encode#Go
+	r0 = []string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"}
+	r1 = []string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"}
+	r2 = []string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"}
+	r3 = []string{"", "M", "MM", "MMM"}
 )
 
 // IntToString converts an integer value to a roman numeral string. An error is
@@ -71,13 +66,13 @@ func IntToBytes(input int) ([]byte, error) {
 // outOfBounds checks to ensure an input value is valid for roman numerals without the need of
 // vinculum (used for values of 4,000 and greater)
 func outOfBounds(input int) bool {
-	return input < _minRoman || input > _maxRoman
+	return input < 1 || input > 3999
 }
 
 func intToRoman(n int) string {
 	// This is efficient in Go. The 4 operands are evaluated,
 	// then a single allocation is made of the exact size needed for the result.
-	return m3[n%1e4/1e3] + m2[n%1e3/1e2] + m1[n%100/10] + m0[n%10]
+	return r3[n%1e4/1e3] + r2[n%1e3/1e2] + r1[n%100/10] + r0[n%10]
 }
 
 // StringToInt converts a roman numeral string to an integer. Roman numerals for numbers
@@ -102,13 +97,13 @@ func BytesToInt(input []byte) (int, error) {
 
 func romanToInt(input []byte) (int, bool) {
 	var output int
-	for _, rom := range _numerals {
+	for _, n := range nums {
-		for bytes.HasPrefix(input, rom.sym) {
+		for bytes.HasPrefix(input, n.sym) {
-			output += rom.val
+			output += n.val
-			input = input[len(rom.sym):]
+			input = input[len(n.sym):]
 		}
 	}
-	// If we are still left with input string values then the
+	// if we are still left with input string values then the
-	// input was invalid and the bool is returned as False
+	// input was invalid and the bool is returned as false
 	return output, len(input) == 0
 }