Embed Directive in Prolog

Here’s the translation of the Go code example to Prolog, formatted in Markdown suitable for Hugo:

Our first example demonstrates how to embed files and folders into a Prolog program. While Prolog doesn’t have a direct equivalent to Go’s embed directive, we can simulate this behavior using Prolog’s file handling capabilities.

:- use_module(library(readutil)).

% Simulate embedding a file's content into a string
file_string(Filename, Content) :-
    read_file_to_string(Filename, Content, []).

% Simulate embedding a file's content into a list of bytes
file_bytes(Filename, Bytes) :-
    read_file_to_codes(Filename, Bytes, []).

% Simulate embedding multiple files
folder_files(Folder, Pattern, Files) :-
    expand_file_name(Pattern, Paths),
    include(exists_file, Paths, Files).

main :-
    % Print out the contents of 'single_file.txt'
    file_string('folder/single_file.txt', FileString),
    write(FileString),
    file_bytes('folder/single_file.txt', FileByte),
    atom_codes(FileByteString, FileByte),
    write(FileByteString),

    % Retrieve some files from the embedded folder
    folder_files('folder', 'folder/*.hash', HashFiles),
    member('folder/file1.hash', HashFiles),
    file_string('folder/file1.hash', Content1),
    write(Content1),
    member('folder/file2.hash', HashFiles),
    file_string('folder/file2.hash', Content2),
    write(Content2).

In this Prolog version:

1. We use the readutil library to read file contents.

2. file_string/2 simulates embedding a file’s content into a string.

3. file_bytes/2 simulates embedding a file’s content into a list of bytes.

4. folder_files/3 simulates embedding multiple files by finding files matching a pattern.

5. In the main/0 predicate, we demonstrate reading file contents and writing them to the console.

To run this example, you would need to create the necessary files and folders:

$ mkdir -p folder
$ echo "hello prolog" > folder/single_file.txt
$ echo "123" > folder/file1.hash
$ echo "456" > folder/file2.hash

Then, you can run the Prolog program:

$ swipl -s embed_example.pl -g main -t halt
hello prolog
hello prolog
123
456

Note that this Prolog version doesn’t actually embed the files into the program at compile time. Instead, it reads the files at runtime. This is because Prolog doesn’t have a built-in mechanism for embedding files at compile time like Go does. However, this approach simulates the behavior in a way that’s idiomatic to Prolog.