Improved speller readability

speller/speller.go

@@ -6,7 +6,7 @@ import (
 	"strings"
 )
 
-var numToDigits = []string{
+var digits = []string{
 	"", "one", "two", "three", "four", "five",
 	"six", "seven", "eight", "nine",
 }
@@ -41,48 +41,46 @@ func Spell(n int64) string {
 	if sign {
 		n = -n
 	}
-	num, digits := strings.Builder{}, digitsReversedSlice(n)
+	num, numDigits := strings.Builder{}, digitsReversedSlice(n)
 	// 35 is the optimal number which gives approx needed
 	// space for the number in 1 allocation
-	num.Grow(len(digits) * 35)
+	num.Grow(len(numDigits) * 35)
 	if sign {
 		num.WriteString("minus ")
 	}
-	largeIndex, iters := 0, 0
-	for i := len(digits) - 1; i >= 0; i, largeIndex = i-3, largeIndex+1 {
-		first, second, third := digits[i-2], digits[i-1], digits[i]
-		if first == 0 && second == 0 && third == 0 {
+	for i, largeIndex := len(numDigits)-1, 0; i >= 0; i, largeIndex = i-3, largeIndex+1 {
+		hundreds, tens, ones := numDigits[i], numDigits[i-1], numDigits[i-2]
+		hundredsPresent, tensPesent, onesPresent := hundreds != 0, tens != 0, ones != 0
+		if !hundredsPresent && !tensPesent && !onesPresent {
 			continue
 		}
-		if iters != 0 {
-			num.WriteRune(' ')
-		}
-		hundreds := numToDigits[third]
-		if hundreds != "" {
-			num.WriteString(hundreds)
+		if hundredsPresent {
+			num.WriteString(digits[hundreds])
 			num.WriteString(" hundred")
-			if second != 0 || first != 0 {
+			if tensPesent || onesPresent {
 				num.WriteRune(' ')
 			}
 		}
-		if second > 1 {
-			num.WriteString(decs[second])
-			if first > 0 {
-				num.WriteRune('-')
-				num.WriteString(numToDigits[first])
-			}
-		} else if second == 1 {
-			num.WriteString(teens[first])
+		if tensPesent {
+			if tens == 1 {
+				num.WriteString(teens[ones])
 			} else {
-			if first > 0 {
-				num.WriteString(numToDigits[first])
+				num.WriteString(decs[tens])
+				if onesPresent {
+					num.WriteRune('-')
 				}
 			}
+		}
+		if onesPresent && tens != 1 {
+			num.WriteString(digits[ones])
+		}
 		if largeIndex < len(large) {
 			num.WriteRune(' ')
 			num.WriteString(large[largeIndex])
 		}
-		iters++
+		num.WriteRune(' ')
 	}
-	return num.String()
+	output := num.String()
+	output = output[:len(output)-1]
+	return output
 }