+redef class Byte
+ # Is `self` a valid hexadecimal digit (in ASCII)
+ #
+ # ~~~nit
+ # intrude import core::bytes
+ # assert not '/'.ascii.to_b.is_valid_hexdigit
+ # assert '0'.ascii.to_b.is_valid_hexdigit
+ # assert '9'.ascii.to_b.is_valid_hexdigit
+ # assert not ':'.ascii.to_b.is_valid_hexdigit
+ # assert not '@'.ascii.to_b.is_valid_hexdigit
+ # assert 'A'.ascii.to_b.is_valid_hexdigit
+ # assert 'F'.ascii.to_b.is_valid_hexdigit
+ # assert not 'G'.ascii.to_b.is_valid_hexdigit
+ # assert not '`'.ascii.to_b.is_valid_hexdigit
+ # assert 'a'.ascii.to_b.is_valid_hexdigit
+ # assert 'f'.ascii.to_b.is_valid_hexdigit
+ # assert not 'g'.ascii.to_b.is_valid_hexdigit
+ # ~~~
+ private fun is_valid_hexdigit: Bool do
+ return (self >= 0x30u8 and self <= 0x39u8) or
+ (self >= 0x41u8 and self <= 0x46u8) or
+ (self >= 0x61u8 and self <= 0x66u8)
+ end
+end
+