Xml in Prolog

Here’s the translation of the XML handling example from Go to Prolog:

% Prolog offers support for XML processing through libraries like sgml

:- use_module(library(sgml)).
:- use_module(library(xpath)).

% Define a structure to represent a plant
plant(Id, Name, Origin) :-
    atom(Id),
    atom(Name),
    is_list(Origin).

% Convert a plant structure to a string representation
plant_to_string(plant(Id, Name, Origin), String) :-
    atomic_list_concat(['Plant id=', Id, ', name=', Name, ', origin=', Origin], String).

% Main predicate
main :-
    % Create a plant structure
    Coffee = plant(27, 'Coffee', ['Ethiopia', 'Brazil']),
    
    % Convert the plant structure to XML
    plant_to_xml(Coffee, CoffeeXML),
    
    % Print the XML
    writeln(CoffeeXML),
    
    % Add XML header
    atom_concat('<?xml version="1.0" encoding="UTF-8"?>\n', CoffeeXML, XMLWithHeader),
    writeln(XMLWithHeader),
    
    % Parse XML back to a plant structure
    load_xml_string(CoffeeXML, XMLDom, []),
    xml_to_plant(XMLDom, ParsedPlant),
    plant_to_string(ParsedPlant, PlantString),
    writeln(PlantString),
    
    % Create another plant
    Tomato = plant(81, 'Tomato', ['Mexico', 'California']),
    
    % Create a nested structure
    nested_plants_to_xml([Coffee, Tomato], NestedXML),
    writeln(NestedXML).

% Convert a plant structure to XML
plant_to_xml(plant(Id, Name, Origin), XML) :-
    format(atom(XML),
           '<plant id="~w">~n  <name>~w</name>~n~w</plant>~n',
           [Id, Name, origins_to_xml(Origin)]).

% Convert origin list to XML
origins_to_xml(Origins) :-
    maplist(origin_to_xml, Origins, OriginXMLs),
    atomic_list_concat(OriginXMLs, '\n', XML).

origin_to_xml(Origin, XML) :-
    format(atom(XML), '  <origin>~w</origin>', [Origin]).

% Convert XML to a plant structure
xml_to_plant(XMLDom, plant(Id, Name, Origin)) :-
    xpath(XMLDom, /(/plant/@id), IdAtom),
    atom_number(IdAtom, Id),
    xpath(XMLDom, /(/plant/name(text)), Name),
    findall(O, xpath(XMLDom, /(/plant/origin(text)), O), Origin).

% Convert a list of plants to nested XML
nested_plants_to_xml(Plants, XML) :-
    maplist(plant_to_xml, Plants, PlantXMLs),
    atomic_list_concat(PlantXMLs, '\n', PlantXMLString),
    format(atom(XML),
           '<nesting>~n  <parent>~n    <child>~n~w    </child>~n  </parent>~n</nesting>~n',
           [PlantXMLString]).

This Prolog code demonstrates XML processing capabilities similar to the original Go example. Here’s a breakdown of the key points:

We use the sgml and xpath libraries for XML processing.
A plant structure is defined to represent plant data.
The main predicate demonstrates various XML operations:
- Creating plant structures
- Converting structures to XML
- Parsing XML back to structures
- Creating nested XML structures
Helper predicates are defined for converting between plant structures and XML representations.
The xpath predicate is used to extract information from parsed XML.

To run this program, you would typically save it in a file (e.g., xml_example.pl) and then load it into a Prolog interpreter. The output would show the various XML representations and parsed data, similar to the Go example.

Note that Prolog’s approach to XML processing is quite different from Go’s, reflecting the language’s logic programming paradigm. The example demonstrates equivalent functionality using Prolog’s declarative style and built-in list processing capabilities.

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