🧠 Logic: 🧵 string_bytes/3 predicate

[ccamel]

Idea

Introduce a new Prolog predicate, string_bytes/3 designed for converting string representations into bytes based on a specified encoding.

This predicate lays the groundwork for the development of further conversion predicates, especially those pertinent to base64 and base58 encodings.

Spec proposal

string_bytes/3 is a predicate that unifies a string with a list of bytes, returning true when the (Unicode) String is
represented by Bytes in Encoding. This predicate should be functionally aligned with the SWI-Prolog implementation (except for errors).

The signature is as follows:

string_bytes(?String, ?Bytes, +Encoding)

Where:

• String is the string to convert to bytes. It can be an Atom, string or list of characters codes.
• Bytes is the list of numbers between 0 and 255 that represent the sequence of bytes.
• Encoding is the encoding to use for the conversion.

Encoding can be one of the following:

• text considers the string as a sequence of Unicode characters.
• octet considers the string as a sequence of bytes.
• utf8 considers the string as a sequence of UTF-8 characters.
• <encoding> considers the string as a sequence of characters in the given encoding.

At least one of String or Bytes must be instantiated.

Examples:

# Convert a string to a list of bytes.
- string_bytes('Hello World', Bytes, octet).

# Convert a list of bytes to a string.
- string_bytes(String, [72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100], octet).