To use this library in your code:
import encoding.hex
hex.decode "f00d" // Evaluates to #[0xf0, 0x0d].
hex.decode "7CAFE" // Evaluates to #[0x07, 0xca, 0xfe].
hex.encode #[0x12, 0x34] // Evaluates to the string "1234".
hex.encode #[0x00, 0x42] // Evaluates to the string "0042".
hex.encode "A*" // Evaluates to the string "412a".
hex.encode #[] // Evaluates to the empty string "".