1== 1 is False?

delphiro delphiro at zonnet.nl
Fri Jun 20 16:07:34 CEST 2003


Hi,

I get a strange error stating that two equal values are not equal. In short what I do;

I calculate the intersection point of two linesegments. If they intersect I check if the intersections point is within both linesegmenents. The code for the latter is;

[CODE]
def GetLineSegmentIntersection( p1, p2, p3, p4 ): 
	p = GetLineIntersection( p1, p2, p3, p4 )
	#do we have an intersection at all?
	if p == []:
		return []
	xmax = _MAX( p1[0], p2[0] )
    	ymax = _MAX( p1[1], p2[1] )
	xmin = _MIN( p1[0], p2[0] )
	ymin = _MIN( p1[1], p2[1] )
   	#within range of line 1?
    	if( p[0] <= xmax )and( p[0] >= xmin)and( p[1] <= ymax )and( p[1] >= ymin ):
        	#line 2
        	xmax = _MAX( p3[0], p4[0] )
        	ymax = _MAX( p3[1], p4[1] )
        	xmin = _MIN( p3[0], p4[0] )
        	ymin = _MIN( p3[1], p4[1] )
		if( p[0] <= xmax )and( p[0] >= xmin)and( p[1] <= ymax )and( p[1] >= ymin ):
       	     		return array((p[0],p[1]))
	#if we get here then the point is not within the linesegments
	return []
[/CODE]

This works fine but for some strange reason I sometimes the statement for the check of line 2 is NOT valid if p[1] == ymax == ymin. 

If I print out the values I get something like 2.260212 <= 2.260212 and 2.260212 >= 2.260212 is NOT true.

What's wrong?
Rob

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