Url Parsing in Modelica

Here’s the translation of the Go URL parsing example to Modelica, formatted in Markdown suitable for Hugo:

model URLParsing
  import Modelica.Utilities.Strings;
  import Modelica.Utilities.System;

  function parseURL
    input String url;
    output String scheme;
    output String user;
    output String password;
    output String host;
    output String port;
    output String path;
    output String fragment;
    output String query;
  algorithm
    // Simple URL parsing implementation
    // Note: This is a basic implementation and may not cover all cases
    scheme := Strings.substring(url, 1, Strings.find(url, "://") - 1);
    
    // Extract user and password
    user := "";
    password := "";
    if Strings.find(url, "@") > 0 then
      user := Strings.substring(url, Strings.find(url, "://") + 3, Strings.find(url, "@") - 1);
      if Strings.find(user, ":") > 0 then
        password := Strings.substring(user, Strings.find(user, ":") + 1);
        user := Strings.substring(user, 1, Strings.find(user, ":") - 1);
      end if;
    end if;
    
    // Extract host and port
    host := Strings.substring(url, Strings.find(url, "@") + 1, Strings.findLast(url, "/") - 1);
    if Strings.find(host, ":") > 0 then
      port := Strings.substring(host, Strings.find(host, ":") + 1);
      host := Strings.substring(host, 1, Strings.find(host, ":") - 1);
    else
      port := "";
    end if;
    
    // Extract path, fragment, and query
    path := Strings.substring(url, Strings.findLast(url, "/"));
    fragment := "";
    query := "";
    if Strings.find(path, "#") > 0 then
      fragment := Strings.substring(path, Strings.find(path, "#") + 1);
      path := Strings.substring(path, 1, Strings.find(path, "#") - 1);
    end if;
    if Strings.find(path, "?") > 0 then
      query := Strings.substring(path, Strings.find(path, "?") + 1);
      path := Strings.substring(path, 1, Strings.find(path, "?") - 1);
    end if;
  end parseURL;

equation
  when initial() then
    // We'll parse this example URL, which includes a scheme, authentication info, 
    // host, port, path, query params, and query fragment.
    String url = "postgres://user:pass@host.com:5432/path?k=v#f";
    
    String scheme, user, password, host, port, path, fragment, query;
    (scheme, user, password, host, port, path, fragment, query) = parseURL(url);
    
    // Print the parsed components
    System.print("Scheme: " + scheme);
    System.print("User: " + user);
    System.print("Password: " + password);
    System.print("Host: " + host);
    System.print("Port: " + port);
    System.print("Path: " + path);
    System.print("Fragment: " + fragment);
    System.print("Query: " + query);
  end when;
end URLParsing;

This Modelica code demonstrates URL parsing, similar to the original example. Here’s an explanation of the key points:

We define a parseURL function that takes a URL string as input and returns various components of the URL.
The parsing is done using string manipulation functions from Modelica.Utilities.Strings, such as substring and find.
We use a when initial() block to execute the parsing and printing once at the start of the simulation.
The URL components are extracted and printed using System.print.

Note that Modelica doesn’t have built-in URL parsing libraries like Go does, so we’ve implemented a basic parsing function. This implementation might not cover all edge cases and is meant for demonstration purposes.

To run this Modelica model, you would typically use a Modelica simulation environment. The output would show the parsed components of the URL, similar to the Go example.

Remember that Modelica is primarily used for modeling and simulation of physical systems, so this URL parsing example is somewhat atypical for the language. In a real-world scenario, you might use Modelica’s external function interface to call a more robust URL parsing library implemented in another language.

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Url Parsing in Modelica