refactor objects

internal/object/str.go

@@ -2,6 +2,7 @@ package object
 
 import (
 	"fmt"
+	"hash/fnv"
 	"strings"
 	"unicode/utf8"
 )
@@ -26,10 +27,18 @@ func (s String) Inspect() string {
 	return fmt.Sprintf("%#v", s.Value)
 }
 
-func (s String) Clone() Object {
+func (s String) Copy() Object {
 	return String{Value: s.Value}
 }
 
+// Hash implements the Hasher interface
+func (s String) Hash() HashKey {
+	h := fnv.New64a()
+	h.Write([]byte(s.Value))
+
+	return HashKey{Type: s.Type(), Value: h.Sum64()}
+}
+
 func (s String) String() string {
 	return s.Value
 }