Sorting By Functions in Modelica

Our example demonstrates how to perform custom sorting in Modelica. We’ll sort strings by their length and a custom data type by a specific field.

model SortingByFunctions
  import Modelica.Utilities.Strings;
  import Modelica.Utilities.Arrays;

  function compareStringLength
    input String a;
    input String b;
    output Integer result;
  algorithm
    result := Integer(Strings.length(a) - Strings.length(b));
  end compareStringLength;

  record Person
    String name;
    Integer age;
  end Person;

  function comparePersonAge
    input Person a;
    input Person b;
    output Integer result;
  algorithm
    result := a.age - b.age;
  end comparePersonAge;

  String[:] fruits = {"peach", "banana", "kiwi"};
  Person[:] people = {
    Person("Jax", 37),
    Person("TJ", 25),
    Person("Alex", 72)
  };

equation
  when initial() then
    // Sort fruits by length
    fruits := Arrays.sort(fruits, compareStringLength);
    Modelica.Utilities.Streams.print("Sorted fruits: " + Strings.toString(fruits));

    // Sort people by age
    people := Arrays.sort(people, comparePersonAge);
    Modelica.Utilities.Streams.print("Sorted people: " + Strings.toString(people));
  end when;

end SortingByFunctions;

In this Modelica example, we implement custom sorting for both strings and a custom data type.

We define a compareStringLength function that compares two strings based on their length. This function is used to sort the fruits array.

For sorting custom types, we define a Person record with name and age fields. We then create a comparePersonAge function to compare Person instances based on their age.

The Arrays.sort function from the Modelica Standard Library is used to perform the sorting. It takes an array and a comparison function as arguments.

When the model is initialized, it sorts the fruits array by string length and the people array by age, then prints the results.

Note that Modelica’s sorting capabilities might be more limited compared to some other languages, and the exact syntax and available functions can vary depending on the Modelica tool or library you’re using.

Also, keep in mind that Modelica is primarily used for modeling and simulation of physical systems, so this sort of data manipulation is not its primary use case. In practice, you might perform such operations in a pre- or post-processing step using a more suitable language.