修正了部分实现

includes/string.vp

@@ -382,4 +382,4 @@ hexdigits: str = "0123456789abcdefABCDEF"
 octdigits: str = "01234567"
 punctuation: str = "!\"#$%&'()*+,-./:;<=>?@[]^_`{|}~"
 whitespace: str = " \t\n\r\f\v"
-printable: str = "01234567890123456789abcdefABCDEF01234567!\"#$%&'()*+,-./:;<=>?@[]^_`{|}~ \t\n\r\f\v"
+printable: str = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~ \t\n\r\f\v"