OMWebBook



Exercise 1

1 Question

Packages are nice to use in Modelica, but what exactly is a package?


1.1

A package is simply a container or namespace for names of classes, functions, constants, and other allowed definitions. A package is also one or the restricted classes.


2 Question

Why use the word encapsulated when creating packages?


2.1

Adding the word encapsulated to the package keeps the package well structured as well as being easier to understand and maintain.


3 Creating a Package

Create a package that contains a constant PI, a type Distance, a function RectangleArea, a function TriangleArea, a function CirclePerimeter and a function CircleArea.


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Write a class, GeometryUser, that uses the package and calls the functions.


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3.1

3.1.1 package Geometry

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loadModel(Modelica)
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package Geometry
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  constant Real PI = 3.1415926536;
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​
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  type Distance = Real(unit = "m");
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​
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  function RectangleArea
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    input Distance B;
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    input Distance H;
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    output Distance area;
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  algorithm
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    area := B*H;
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  end RectangleArea;
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​
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​
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  function TriangleArea
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    input Distance B;
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    input Distance H;
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    output Distance area;
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  algorithm
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    area := RectangleArea(B, H)/2;
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  end TriangleArea;
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​
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​
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  function CirclePerimeter
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    input Distance radius;
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    output Distance perimeter;
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  algorithm
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    perimeter := 2*PI*radius;
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  end CirclePerimeter;
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​
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​
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  function CircleArea
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    input Distance radius;
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    output Distance area;
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  algorithm
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     area := PI*radius^2;
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  end CircleArea;
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​
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end Geometry;
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3.1.2 GeometryUser

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class GeometryUser
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  Geometry.Distance rectangleArea   = Geometry.RectangleArea(4, 5);
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  Geometry.Distance triangleArea    = Geometry.TriangleArea(4, 5);
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  Geometry.Distance circlePerimeter = Geometry.CirclePerimeter(3.5);
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  Geometry.Distance circleArea      = Geometry.CircleArea(3.5);
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end GeometryUser;
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3.1.3 Simulation of GeometryUser

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simulate( GeometryUser )
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{val(rectangleArea,0), val(triangleArea,0),
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val(circlePerimeter,0),val(circleArea,0)}
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