Evaluate if and return, error validation.

Signed-off-by: jmug <u.g.a.mariano@gmail.com>

pkg/object/object.go

@@ -5,9 +5,11 @@ import "fmt"
 type ObjectType string
 
 const (
-	INTEGER_OBJ = "INTEGER"
-	BOOLEAN_OBJ = "BOOLEAN"
-	NULL_OBJ    = "NULL"
+	INTEGER_OBJ      = "INTEGER"
+	BOOLEAN_OBJ      = "BOOLEAN"
+	NULL_OBJ         = "NULL"
+	RETURN_VALUE_OBJ = "RETURN"
+	ERROR_OBJ        = "ERROR"
 )
 
 type Object interface {
@@ -45,3 +47,25 @@ func (n *Null) Type() ObjectType {
 func (n *Null) Inspect() string {
 	return "null"
 }
+
+type ReturnValue struct {
+	Value Object
+}
+
+func (rv *ReturnValue) Type() ObjectType {
+	return RETURN_VALUE_OBJ
+}
+func (rv *ReturnValue) Inspect() string {
+	return rv.Value.Inspect()
+}
+
+type Error struct {
+	Message string
+}
+
+func (e *Error) Type() ObjectType {
+	return ERROR_OBJ
+}
+func (e *Error) Inspect() string {
+	return "ERROR: " + e.Message
+}