File Paths in Modelica

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

The Modelica.Utilities.Files package provides functions to parse and construct file paths in a way that is portable between operating systems.

model FilePaths
  import Modelica.Utilities.Files;
  import Modelica.Utilities.Strings;

  function main()
    String p;
    String ext;
    String rel;
  algorithm
    // Join should be used to construct paths in a portable way
    p := Files.fullPathName(Files.join("dir1", "dir2", "filename"));
    Modelica.Utilities.Streams.print("p: " + p);

    // You should always use join instead of concatenating separators manually
    Modelica.Utilities.Streams.print(Files.fullPathName(Files.join("dir1//", "filename")));
    Modelica.Utilities.Streams.print(Files.fullPathName(Files.join("dir1/../dir1", "filename")));

    // We can split a path to the directory and the file
    Modelica.Utilities.Streams.print("Dir(p): " + Files.dirName(p));
    Modelica.Utilities.Streams.print("Base(p): " + Files.baseName(p));

    // We can check whether a path is absolute
    Modelica.Utilities.Streams.print(String(Files.isAbsolute("dir/file")));
    Modelica.Utilities.Streams.print(String(Files.isAbsolute("/dir/file")));

    // Some file names have extensions following a dot
    ext := Files.extension("config.json");
    Modelica.Utilities.Streams.print(ext);

    // To find the file's name with the extension removed
    Modelica.Utilities.Streams.print(Strings.substring("config.json", 1, Strings.length("config.json") - Strings.length(ext)));

    // Rel finds a relative path between a base and a target
    rel := Files.relativePath("a/b", "a/b/t/file");
    Modelica.Utilities.Streams.print(rel);

    rel := Files.relativePath("a/b", "a/c/t/file");
    Modelica.Utilities.Streams.print(rel);
  end main;

equation
  main();
end FilePaths;

To run this Modelica model, you would typically use a Modelica simulation environment. The output would be similar to the following:

p: /path/to/current/directory/dir1/dir2/filename
/path/to/current/directory/dir1/filename
/path/to/current/directory/dir1/filename
Dir(p): /path/to/current/directory/dir1/dir2
Base(p): filename
false
true
.json
config
t/file
../c/t/file

Note that Modelica doesn’t have a direct equivalent to Go’s filepath package, so we’re using the Modelica.Utilities.Files package which provides similar functionality. The Files.fullPathName function is used to ensure absolute paths are returned, as Modelica typically works with absolute paths.

Also, Modelica doesn’t have a built-in function to check if a path is absolute, so the isAbsolute function is simulated here. In a real Modelica environment, you might need to implement this function yourself or use a library that provides it.

The relativePath function in Modelica might behave differently from Go’s filepath.Rel, especially for paths that go up in the directory hierarchy. The exact behavior would depend on the specific Modelica implementation.

Remember that file operations in Modelica are often more restricted than in general-purpose programming languages like Go, as Modelica is primarily designed for modeling and simulation rather than general file system operations.

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File Paths in Modelica