Add isNegative() to the Type\NumberInterface

src/Type/Decimal.php

@@ -37,6 +37,11 @@ final class Decimal implements NumberInterface
      */
     private $value;
 
+    /**
+     * @var bool
+     */
+    private $isNegative = false;
+
     /**
      * @param mixed $value The decimal value to store
      */
@@ -61,9 +66,18 @@ final class Decimal implements NumberInterface
             $value = '0';
         }
 
+        if (strpos($value, '-') === 0) {
+            $this->isNegative = true;
+        }
+
         $this->value = $value;
     }
 
+    public function isNegative(): bool
+    {
+        return $this->isNegative;
+    }
+
     public function toString(): string
     {
         return $this->value;

src/Type/Integer.php

@@ -40,6 +40,11 @@ final class Integer implements NumberInterface
      */
     private $value;
 
+    /**
+     * @var bool
+     */
+    private $isNegative = false;
+
     /**
      * @param mixed $value The integer value to store
      */
@@ -72,11 +77,17 @@ final class Integer implements NumberInterface
         // Add the negative sign back to the value.
         if ($sign === '-' && $value !== '0') {
             $value = $sign . $value;
+            $this->isNegative = true;
         }
 
         $this->value = $value;
     }
 
+    public function isNegative(): bool
+    {
+        return $this->isNegative;
+    }
+
     public function toString(): string
     {
         return $this->value;

src/Type/NumberInterface.php

@@ -21,4 +21,8 @@ namespace Ramsey\Uuid\Type;
  */
 interface NumberInterface extends TypeInterface
 {
+    /**
+     * Returns true if this number is less than zero
+     */
+    public function isNegative(): bool;
 }