Extern doesn't work?

Import "Line2D.cpp"


Public

Extern "win32"
	Function CreateLine:Int( x1#,y1#,x2#,y2# )="CreateLine"
	Function SetLine( line,x1#,y1#,x2#,y2# )
	Function LineCast:Int( line1,line2,result )
	Function ResultX:Int(result)
	Function ResultY:Int(result)
	Function CreateResult:Int()
	
End Extern



Graphics 640,480,0

Local x1#,y1#,x2#,y2#

x1=20
y1=20

Local lin1,lin2

lin1 = createLine( x1,y1,x2,y2 )
lin2 = createLine( 320,0,325,480 )

If lin1=0 RuntimeError "Line was not created."

Repeat
Cls
	x2=MouseX()
	y2=MouseY()	
	
	DrawLine x1,y1,x2,y2
	DrawLine 320,0,325,480
Flip
Until KeyDown(1)

class XPOINT
{
public:
float x, y;
};

class XLINE
{
public:
XPOINT o, p;
float m;
float c;
};

float min( float v1,float v2 )
{
     if(v1<v2) return v2;
     return v1;
}

float max( float v1,float v2) 
{
     if(v1>v2) return v1;
     return v2;
}

XLINE CreateLine( float x1,float y1,float x2,float y2){
   XLINE out;
   out.o.x=x1;
   out.o.y=y1;
   out.p.x=x2;
   out.p.y=y2;
   return out;
}

void SetLine( XLINE &l,float x1,float y1,float x2,float y2){
    l.o.x=x1;
    l.o.y=y1;
    l.p.x=x2;
    l.p.y=y2;
}


XPOINT * CreateResult(){
   return( new XPOINT);
}

float ResultX( XPOINT *i){
   return i->x;
}

float ResultY( XPOINT *i){
  return i->y;
}



int LineCast( XLINE &a, XLINE &b, XPOINT *i )
{
// null width lines cannot intercept
if ( (a.p.x == a.o.x) || (b.p.x == b.o.x) )
{
return false;
}
// calculate gradients
a.m = (a.p.y - a.o.y) / (a.p.x - a.o.x);
b.m = (b.p.y - b.o.y) / (b.p.x - b.o.x);
// parallel lines can't intercept
if (a.m == b.m)
{
return false;
}
// calculate axis intersect values
a.c = a.o.y - (a.m * a.o.x);
b.c = b.o.y - (b.m * b.o.x);
// calculate x point of intercept
i->x = (b.c - a.c) / (a.m - b.m);
// is intersection point in segment
if ( i->x < min(a.o.x, a.p.x) || i->x > max(a.o.x, a.p.x) )
{
return false;
}
if ( i->x < min(b.o.x, b.p.x) || i->x > max(b.o.x, b.p.x) )
{
return false;
}
// calculate y point of intercept
i->y = (a.m * i->x) + a.c;
// points intercept
return true;
};

extern "C" XLINE CreateLine( float x1,float y1,float x2,float y2){
   XLINE out;
   out.o.x=x1;
   out.o.y=y1;
   out.p.x=x2;
   out.p.y=y2;
   return out;
}

extern "C" XLINE CreateLine( float x1,float y1,float x2,float y2)

Function CreateLine:Int( x1#,y1#,x2#,y2# )="_Z10CreateLineffff"

Function Lines_Intersect(Ax#, Ay#, Bx#, By#, Cx#, Cy#, Dx#, Dy#)
	Local Rn# = (Ay#-Cy#)*(Dx#-Cx#) - (Ax#-Cx#)*(Dy#-Cy#)
    Local Rd# = (Bx#-Ax#)*(Dy#-Cy#) - (By#-Ay#)*(Dx#-Cx#)
	Print RD+":"+rn
	If Rd# = 0
		Return False
	Else
         Local Sn# = (Ay#-Cy#)*(Bx#-Ax#) - (Ax#-Cx#)*(By#-Ay#)
		 Intersection_AB# = Rn# / Rd#
         Intersection_CD# = Sn# / Rd#
         Intersection_X# = Ax# + Intersection_AB#*(Bx#-Ax#)
         Intersection_Y# = Ay# + Intersection_AB#*(By#-Ay#)
    Return True
    EndIf
End Function

Function Lines_Intersect(Ax#,Ay#,Bx#,By#,Cx#,Cy#,Dx#,Dy#)
  

	Rn#=(Ay#-Cy#)*(Dx#-Cx#)-(Ax#-Cx#)*(Dy#-Cy#)
	Rd#=(Bx#-Ax#)*(Dy#-Cy#)-(By#-Ay#)*(Dx#-Cx#)
	If Rd# = 0 
		; Lines are parallel.
		; If Rn# is also 0 then lines are coincident.  All points intersect. 
		; Otherwise, there is no intersection point.
		Return False
	Else
		; The lines intersect at some point.  Calculate the intersection point.
		Sn# = (Ay#-Cy#)*(Bx#-Ax#) - (Ax#-Cx#)*(By#-Ay#)
		Intersection_AB# = Rn# / Rd#
		Intersection_CD# = Sn# / Rd#
		
		; MAKE SURE IT FITS WITHIN THE FIRST LINE
		If Intersection_AB#<0.0 Or Intersection_AB#>1.0	
			; THEY INTERSECT, BUT BEYOND THE LENGTH OF LINE 2.
			Return False
		Else
			; MAKE SURE IT FITS WITHIN THE SECOND LINE
			If Intersection_CD#<0.0 Or Intersection_CD#>1.0
				Return False
			Else
				Intersection_X# = Ax# + Intersection_AB#*(Bx#-Ax#)
				Intersection_Z# = Ay# + Intersection_AB#*(By#-Ay#)	
				Return True		
			End If
		End If
	EndIf

End Function

Graphics 640,480,0
 
Local a:Vector2=New Vector2
Local b:Vector2=New Vector2
Local c:Vector2=New Vector2
Local d:Vector2=New Vector2

Local i:Vector2=New Vector2

a.x=34
a.y=62
b.x=42
b.y=87

c.x=50
c.y=0
d.x=43
d.y=100

While Not KeyHit(KEY_ESCAPE)
	
	'Draw a circle
	
	DrawLine a.x,a.y,b.x,b.y
	DrawLine c.x,c.y,d.x,d.y
	
	If (linesIntersect2D(a,b,c,d,Null))
		DrawText "Lines Intersect",300,300
	Else
		DrawText "No Intersection",300,300
	End If

	Flip
	Cls
	
	FlushMem
End While


Type Vector2
	Field x:Float
	Field y:Float
	
End Type

Type Vector3 Extends Vector2
	Field z:Float
End Type


'Tests for the intersection of two lines in 2 dimensions.  Each line is defined by a start and an end point.
'Returns True if the lines intersect or false otherwise.  If they do intersect, outIntersect
'is set to the coordinates of the intersection.  outIntersect can be Null.

Function linesIntersect2D(p1:Vector2,p2:Vector2,p3:Vector2,p4:Vector2, outIntersect:Vector2)

	'Eqn of two lines:
	'	lineA = p1 + uA(p2-p1)
	'	lineB = p3 + uB(p4-p3)
	
	'Put lineA = lineB, and solve for uA, gives us:	

	uA:Float=	((p4.x-p3.x)*(p1.y-p3.y)) - ((p4.y-p3.y)*(p1.x-p3.x))
	temp:Float= ((p4.y-p3.y)*(p2.x-p1.x)) - ((p4.x-p3.x)*(p2.y-p1.y))
	
	uB:Float =  ((p2.x-p1.x)*(p1.y-p3.y)) - ((p2.y-p1.y)*(p1.x-p3.x))
	
	
	'Check if lines are parallel
	If (temp=0)
		Return False
	End If
	
	uA :/ temp
	uB :/ temp
	
	intersectX:Float = p1.x+uA*(p2.x-p1.x)
	intersectY:Float = p1.y+uA*(p2.y-p1.y)
	
	If ((uA >= 0) And (uA <= 1) And (uB >= 0) And (uB <= 1))	
		If (outIntersect)
			outIntersect.x=intersectX
			outIntersect.y=intersectY
		End If
		
		Return True
	Else
		Return False
	End If

End Function