``````(* ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
³ Programated by Vladimir Zahoransky                        ³
³                Vladko software                            ³
³ Contact      : zahoran@cezap.ii.fmph.uniba.sk             ³
³ Program tema : Line in direction version                  ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ *)

{
This program draw the Line in direction version. In this version do not
exist line, wich can be not writed how function. If a=0 (line direction)
then it is line paraller with x-coordination. This program can not draw
(the direction version) the line paraller with y-coordination. This know
graph05.pas. This version will be if a come to infinity.
How work this program ? Active coordinate system. Then init the
parameters for function relation : y=a*x+b (or y=k*x+q)

If a=0 and b=0  then line = x-coordination
If a=0 and b<>0 then line is paraller with x-coordination
If a<>0 and b=0 then point [0,0] is in line
If a<>0 and b<>0 then line have not [0,0]

IF b=0 or b<>0 is not a problem and don't make some problems.
If a=0 then it is so problem, because for extreme points (y=-240, y=240)
in relation :    240 + b    (and for a=0 it is infinity)
- -------
a

If a>0 then the line is increasive
If a<0 then the line is decreasive

b is just the move of line : b>0 up
b<0 down

If sometimes is message Division by zero - it is problem with relation :
-50+random(100)
---------------
-50+random(100)

If random=50 in denominator then -50+50=0 and this make this message.
}

Uses Okor;

Type Mygraph=Object(kor)
Procedure Init;
Procedure Coordinate_system;
End;

Procedure Mygraph.Init;
Begin
kor.init(0,0,0);
End;

Procedure Mygraph.Coordinate_system;
Var i:integer;
Begin
ZmenFp(15);
PresunXY(-320,0);
ZmenXY(320,0);
PresunXY(315,5);
ZmenXY(320,0);
ZmenXY(315,-5);
PresunXY(310,-10);
Pis('x');

PresunXY(0,-240);;
ZmenXY(0,240);
PresunXY(-5,235);
ZmenXY(0,240);
ZmenXY(5,235);
PresunXY(8,230);
Pis('y');

For i:=0 to 32 do Begin
PresunXY(-320+20*i,-3);
ZmenXY(-320+20*i,3);
End;

For i:=0 to 23 do Begin
PresunXY(-3,-240+20*i);
ZmenXY(3,-240+20*i);
End;

End;

Type Analytical_line=Object(kor)
a,b:real;
Procedure Init(a1,b1:real);
Procedure Draw_line;
End;

Procedure Analytical_line.Init;
Begin
a:=a1;
b:=b1;
If a<>0 Then kor.Init( (-240-b1)/a1,-240,0)
Else kor.Init(-320,b1,0);
End;

Procedure Analytical_line.Draw_line;
Begin
If a<>0 Then ZmenXY((240-b)/a,240)
Else ZmenXY(320,b);
End;

Var Mg:MyGraph;
Al:Analytical_line;
I:integer;
Begin

With Mg do Begin
Init;
Coordinate_system;
End;
Randomize;
With Al Do
For i:=1 to 10 do Begin
init((-50+random(100))/(-50+random(100)),
-100+random(200));
ZmenFp(1+ i mod 14);
Draw_line;
CakajKlaves;
Koniec;
End;

End.

``````