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Predicate hex_bytes/2
Availability::- use_module(library(crypto)).(can be autoloaded)
Source[det]hex_bytes(?Hex, ?List)
Relation between a hexadecimal sequence and a list of bytes. Hex is an atom, string, list of characters or list of codes in hexadecimal encoding. This is the format that is used by crypto_data_hash/3 and related predicates to represent hashes. Bytes is a list of integers between 0 and 255 that represent the sequence as a list of bytes. At least one of the arguments must be instantiated. When converting List to Hex, an atom is used to represent the sequence of hexadecimal digits.

Example: 

?- hex_bytes('501ACE', Bs).
Bs = [80, 26, 206].
See also
base64_encoded/3 for Base64 encoding, which is often used to transfer or embed binary data in applications.
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LogicalCaptain said (2021-05-23T09:00:43):0 upvotes 0 0 downvotes
Picture of user LogicalCaptain.

If you want to print a nmuber in hexadecimal though, just ise format/2:

0-padded 4 nibbles:

?- Code=6464, format(atom(T),"0x~|~`0t~16r~4+",[Code]).
Code = 6464,
T = '0x1940'.