added negative support

CHANGELOG

@@ -1,2 +1,5 @@
+v1.0.2, released 2024-08-08 
+    * support negative values
+
 v1.0.1, released 2024-08-08 
     * fix encoding to zero

abcex.go

@@ -38,23 +38,42 @@ func Encode(number int64) string {
 	}
 
 	result := ""
+	negative := false
+	if number < 0 {
+		number = number * (-1)
+		negative = true
+	}
 
 	for number > 0 {
 		result = fmt.Sprintf("%s%s", decToAbcex[int(number%36)], result)
 		number /= 36
 	}
 
+	if negative {
+		return "-" + result
+	}
+
 	return result
 }
 
 func Decode(str string) int64 {
 	var result int64
 	result = 0
+	negative := false
+	if string(str[0]) == "-" {
+		negative = true
+		str = str[1:]
+	}
+
 	str = reverse(str)
 
 	for i, c := range str {
 		result = int64(math.Pow(36, float64(i)))*int64(abcexToDec[string(c)]) + result
 	}
 
+	if negative {
+		return result * (-1)
+	}
+
 	return result
 }

abcex_test.go

@@ -1,24 +1,37 @@
 package abcex
 
 import (
-	"fmt"
 	"testing"
 )
 
 func TestEncode(t *testing.T) {
-	fmt.Println(Encode(12345))
+	if Encode(12345) != "9ix" {
-	// Output: 9ix
+		t.Fatal("Failed encoding")
+	}
 }
 
 func TestDecode(t *testing.T) {
-	fmt.Println(Decode("9ix"))
+	if Decode("9ix") != 12345 {
-	// Output: 12345
+		t.Fatal("Failed decoding")
+	}
 }
 
 func TestZero(t *testing.T) {
-	fmt.Println(Encode(0))
+	if Encode(0) != "0" {
-	// Output: 0
+		t.Fatal("Failed zero encoding")
+	}
 
-	fmt.Println(Decode("0"))
+	if Decode("0") != 0 {
-	// Output: 0
+		t.Fatal("Failed zero decoding")
+	}
+}
+
+func TestNegative(t *testing.T) {
+	if Encode(-20) != "-k" {
+		t.Fatal("Failed negative encoding:", Encode(-20))
+	}
+
+	if Decode("-ab") != -371 {
+		t.Fatal("Failed negative decoding", Decode("-ab"))
+	}
 }