Checkpoint

src/prolog/ast/terms/AnonymousVariable.kt

@@ -0,0 +1,17 @@
+package prolog.ast.terms
+
+import io.Logger
+
+class AnonymousVariable(id: Int) : Variable("_$id") {
+    companion object {
+        private var counter = 0
+        fun create(): AnonymousVariable {
+            val id = counter
+            counter++
+            Logger.debug("Creating anonymous variable: _${id}")
+            return AnonymousVariable(id)
+        }
+    }
+
+    override fun toString(): String = "_"
+}

src/prolog/ast/terms/Variable.kt

@@ -6,7 +6,7 @@ import prolog.ast.arithmetic.Expression
 import prolog.ast.arithmetic.Simplification
 import prolog.ast.logic.LogicOperand
 
-data class Variable(val name: String) : Term, Body, Expression, LogicOperand() {
+open class Variable(val name: String) : Term, Body, Expression, LogicOperand() {
     override fun simplify(subs: Substitutions): Simplification {
         // If the variable is bound, return the value of the binding
         // If the variable is not bound, return the variable itself
@@ -28,5 +28,15 @@ data class Variable(val name: String) : Term, Body, Expression, LogicOperand() {
         return sequenceOf(Result.failure(IllegalArgumentException("Unbound variable: $this")))
     }
 
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other == null || other !is Variable) return false
+        return name == other.name
+    }
+
+    override fun hashCode(): Int {
+        return name.hashCode()
+    }
+
     override fun toString(): String = name
 }