Add instance methods to JsonPointer for platform without extensions

Author: Oleg

src/commonMain/kotlin/com/github/optimumcode/json/pointer/JsonPointer.kt

@@ -20,6 +20,46 @@ public sealed class JsonPointer(
   internal val next: JsonPointer? = null,
 ) {
 
+  /**
+   * Creates a new [JsonPointer] that points to an [index] in the array.
+   *
+   * Example:
+   * ```kotlin
+   * val pointer = JsonPointer("/test").atIndex(0) // "/test/0"
+   * ```
+   */
+  public fun atIndex(index: Int): JsonPointer =
+    JsonPointer(
+      buildString {
+        val pointer = this@JsonPointer.toString()
+        append(pointer)
+        if (!pointer.endsWith(SEPARATOR)) {
+          append(SEPARATOR)
+        }
+        append(index)
+      },
+    )
+
+  /**
+   * Creates a new [JsonPointer] that points to a [property] passed as a parameter.
+   *
+   * Example:
+   * ```kotlin
+   * val pointer = JsonPointer.ROOT.atProperty("prop1").atProperty("prop2")  // "/prop1/prop2"
+   * ```
+   */
+  public fun atProperty(property: String): JsonPointer =
+    JsonPointer(
+      buildString {
+        val pointer = this@JsonPointer.toString()
+        append(pointer)
+        if (!pointer.endsWith(SEPARATOR)) {
+          append(SEPARATOR)
+        }
+        append(property)
+      },
+    )
+
   override fun toString(): String {
     return if (pathOffset <= 0) {
       fullPath

src/commonMain/kotlin/com/github/optimumcode/json/pointer/extensions.kt

@@ -18,17 +18,7 @@ import kotlin.jvm.JvmName
  * val index = pointer[0] // "/test/0"
  * ```
  */
-public operator fun JsonPointer.get(index: Int): JsonPointer =
-  JsonPointer(
-    buildString {
-      val pointer = this@get.toString()
-      append(pointer)
-      if (!pointer.endsWith(JsonPointer.SEPARATOR)) {
-        append(JsonPointer.SEPARATOR)
-      }
-      append(index)
-    },
-  )
+public operator fun JsonPointer.get(index: Int): JsonPointer = atIndex(index)
 
 /**
  * Creates a new [JsonPointer] that points to a [property] passed as a parameter.
@@ -39,17 +29,7 @@ public operator fun JsonPointer.get(index: Int): JsonPointer =
  * val pointer = JsonPointer.ROOT / "prop1" / "prop2"  // "/prop1/prop2"
  * ```
  */
-public operator fun JsonPointer.div(property: String): JsonPointer =
-  JsonPointer(
-    buildString {
-      val pointer = this@div.toString()
-      append(pointer)
-      if (!pointer.endsWith(JsonPointer.SEPARATOR)) {
-        append(JsonPointer.SEPARATOR)
-      }
-      append(property)
-    },
-  )
+public operator fun JsonPointer.div(property: String): JsonPointer = atProperty(property)
 
 /**
  * Appends [otherPointer] to the current [JsonPointer].