The Sinclair QL Forum

Code: Select all

{ 
  Program to demonstrate classes on the QL. 

  This example blatently copied from:
  https://www.tutorialspoint.com/pascal/pascal_classes.htm

  A few minor amendments and extra comments by Norm.
}


{$mode objfpc}    // directive to be used for defining classes
{$m+}             // directive to be used for using constructor


{ 
  Define the class... 
}
type
   Rectangle = class
   const 
      minWidth = 2;
      minHeight = 2;

   private
      height, width: integer;
      procedure drawTopBottom;
      procedure drawMiddle;
   
   public
      constructor create(h, w: integer);
      procedure setheight(h: integer);
      
      function getheight(): integer;
      procedure setwidth(w: integer);
      
      function getwidth(): integer;
      procedure draw;
end;


var
   { 
     r1 is a reference to a Rectangle class instance 
   }
   r1: Rectangle;


{ 
  We need a constructor for the class. Create is "standard". Mostly! 
}
constructor Rectangle.create(h, w: integer);
begin
   {
     We can just assign the passed values to height and
     width, but we would like to carry out some validation
     to keep them withing acceptable bounds.
   }
   setheight(h);
   setwidth(w);
end;

{ 
  We have a few functions to help set stuff. 
}
procedure Rectangle.setheight(h: integer);
begin
   if (height < minHeight) then
      height := minHeight
   else
      height := h;
end;

procedure Rectangle.setwidth(w: integer);
begin
   if (width < minWidth) then
      width := minWidth
   else
      width := w;
end;

{ 
  We have a few functions to help get stuff. 
}
function Rectangle.getheight(): integer;
begin
   getheight := height;
end;

function Rectangle.getwidth(): integer;
begin
   getwidth := width;
end;

{ 
  And a few procedures to draw a rectangle. I say "draw".... 
}

procedure Rectangle.drawTopBottom;
var i: integer;
begin
   write('+');
   for i := 1 to width - 2 do
      write('-');
   writeln('+');
end;

procedure Rectangle.drawMiddle;
var i, j: integer;
begin
   for i := 1 to height - 2 do
   begin
      write('|');
      for j := 1 to width - 2 do
         write(' ');
      writeln('|');
   end; 
end;

procedure Rectangle.draw;
begin
   { Top line. }
   drawTopBottom;

   { Middle of rectangle. }
   drawMiddle;

   { Bottom line. }
   drawTopBottom;
	   
end;

{
  The actual program starts here. 
  We create a new rectangle and assign it to r1, it gets its
  width and height from the constructor. After drawing it,
  change the width and height and draw the new rectangle.
}
begin
   {
     This will be adjusted to 2 by 2. Minimum sizes apply.
   }
   r1:= Rectangle.create(1, 1);
   writeln(' Draw Rectangle: ', r1.getheight(), ' by ' , r1.getwidth());
   r1.draw;

   r1.setheight(5);
   r1.setwidth(7);
   writeln(' Draw Rectangle: ', r1.getheight(), ' by ' , r1.getwidth());
   r1.draw;

   r1.setwidth(10);
   writeln(' Draw Rectangle: ', r1.getheight(), ' by ' , r1.getwidth());
   r1.draw;
end.

Code: Select all

 Draw Rectangle: 2 by 2
++
++
 Draw Rectangle: 5 by 7
+-----+
|     |
|     |
|     |
+-----+
 Draw Rectangle: 5 by 10
+--------+
|        |
|        |
|        |
+--------+
Press any key to exit.

Code: Select all

110 exe$ = 'program_name'
120 dos$ = 'dos1_' & exe$ & '.exe'
130 ram$ = 'ram1_' & exe$
140 :
150 copy_o dos$ to ram$
160 ex xtcc_xtcc_bin, ram$
170 :
180 cls
190 ex ram$
200 stop