Divide by Zero in PerpendicDistSqrd (Delphi)

[olivergrahl]

Glad I found this great library, thanks for providing it!

Here's a problem in the Delphi code (Clipper v2.0.1):

In

Clipper2/Delphi/Clipper2Lib/Clipper.pas

Lines 840 to 851 in 20f05b4

	function PerpendicDistSqrd(const pt, line1, line2: TPoint64): double;
	{$IFDEF INLINE} inline; {$ENDIF}
	var
	a,b,c,d: double;
	begin
	a := pt.X - line1.X;
	b := pt.Y - line1.Y;
	c := line2.X - line1.X;
	d := line2.Y - line1.Y;
	result := Iif((c = 0) and (d = 0),
	0, Sqr(a * d - c * b) / (c * c + d * d));
	end;

  result := Iif((c = 0) and (d = 0),
    0, Sqr(a * d - c * b) / (c * c + d * d));

should be

  if (c = 0) and (d = 0) then
    result := 0
  else
    result := Sqr(a * d - c * b) / (c * c + d * d);

or

  if (c = 0) and (d = 0) then
    exit(0);

  result := Sqr(a * d - c * b) / (c * c + d * d);

Background: Iif is just a function, not a coalesce operator like eval ? true : false. Both expressions used as params to Iif get evaluated, so Iif cannot be used to avoid division by zero here.

There are other questionable uses of Iif in the code, where at least for performance reasons, Iif should better be replaced by real if .. then .. else constructs.