Classes

[Gintaras]

The Classes topic in QM help is for those that already know what is a class. Most programming languages have classes.

To understand user-defined classes, you have to be familiar with variables, user-defined types and user-defined functions. A class is an user-defined type that also has functions.

Let's create a simple rectangle class. Class definition includes class name and member variables.

Macro

Code:

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class CRect
,double'm_width
,double'm_height

Put it in some macro and compile or run the macro. It lets QM know about the new class. To make it always available, put it in a function that runs at startup. For example, in init2 (create it if does not exist).

Now create 3 member functions. To add member functions use menu File -> New -> New Member Function. The item name consists of class name, . and function name.

Member function CRect.Init

Code:

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function double'width double'height

;Initializes the variable.


m_width=width
m_height=height

Member function CRect.Area

Code:

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function'double

;Calculates rectangle area.


ret m_width*m_height

Member function CRect.Hypotenuse

Code:

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function'double

;Calculates rectangle hypothenuse.
;It is distance between two opposite corners.


ret _hypot(m_width m_height)

Now the class is created and you can use it anywhere. Declare variables of CRect type and call functions using syntax variable.Function(arguments).

Macro

Code:

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CRect r.Init(10 20)
out r.Area
out r.Hypotenuse

CRect r2.Init(11 19)
if(r2.Area>r.Area) out "r2 is bigger"
else out "r is bigger"