Done with the book! Added hash maps and the puts builtin.

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

pkg/evaluator/builtins.go

@@ -1,12 +1,21 @@
 package evaluator
 
 import (
+	"fmt"
 	"os"
 
 	"code.jmug.me/jmug/interpreter-in-go/pkg/object"
 )
 
 var builtins = map[string]*object.Builtin{
+	"puts": {
+		Fn: func(args ...object.Object) object.Object {
+			for _, arg := range args {
+				fmt.Println(arg.Inspect())
+			}
+			return _NULL
+		},
+	},
 	"len": {
 		Fn: func(args ...object.Object) object.Object {
 			if len(args) != 1 {