feat: Implement eval methods for expressions

lib/syntax/UnaryOperators.ml

@@ -1,5 +1,40 @@
-type unary_operators = ArithmeticNegation | LogicalNegation
+class virtual unaryOperator =
+  object
+    inherit Node.node
+    method virtual check_type : Types.t -> Types.t
+    method virtual eval : Literals.literal_value -> Literals.literal_value
+  end
 
-let pp_unary_operators = function
-  | ArithmeticNegation -> "ArithmeticNegation"
-  | LogicalNegation -> "LogicalNegation"
+class arithmeticNegation =
+  object
+    inherit unaryOperator
+    method to_string = "ArithmeticNegation"
+
+    method check_type (operand : Types.t) =
+      match operand with
+      | Types.IntegerType -> Types.IntegerType
+      | Types.FloatType -> Types.FloatType
+      | _ -> raise (Failure "ArithmeticNegation: operand must be a number")
+
+    method eval operand =
+      match operand with
+      | `Int i -> `Int (-i)
+      | `Float f -> `Float (-.f)
+      | _ -> raise (Failure "ArithmeticNegation: operand must be a number")
+  end
+
+class logicalNegation =
+  object
+    inherit unaryOperator
+    method to_string = "LogicalNegation"
+
+    method check_type (operand : Types.t) =
+      match operand with
+      | Types.BooleanType -> Types.BooleanType
+      | _ -> raise (Failure "LogicalNegation: operand must be a boolean")
+
+    method eval operand =
+      match operand with
+      | `Bool b -> `Bool (not b)
+      | _ -> raise (Failure "LogicalNegation: operand must be a boolean")
+  end