fn main() {
let mut val = b'A';
println!("{}", val.is_ascii_hexdigit());
val = b'a';
println!("{}", val.is_ascii_hexdigit());
val = b'0';
println!("{}", val.is_ascii_hexdigit());
val = b'\n';
println!("{}", val.is_ascii_hexdigit());
}
/*
run:
true
true
true
false
*/