added some tests with an empty ellipse

src/Geometry-Tests/GEllipseTest.class.st

@@ -12,6 +12,12 @@ GEllipseTest >> actualClass [
 	^ GEllipse
 ]
 
+{ #category : #util }
+GEllipseTest >> sortedIntersectionsBetween: shape and: line [
+	^ (shape intersectionsWith: line) asOrderedCollection 
+		sorted: [ :a :b | a asPoint < b asPoint ].
+]
+
 { #category : #tests }
 GEllipseTest >> testArea [
 	ellipse := GEllipse center: 5 , -1 vertex: 10 , -1 coVertex: 5 , 2.
@@ -29,6 +35,30 @@ GEllipseTest >> testBoundaryContains [
 	self deny: (ellipse boundaryContains: 3, 0.13).
 ]
 
+{ #category : #tests }
+GEllipseTest >> testEmpty [
+	| shape line intersections |
+	shape := GEllipse center: 0@0 vertex: 0@0 coVertex: 0@0.
+	line := GLine through: shape center and: 10@10.
+	intersections := self sortedIntersectionsBetween: shape and: line.
+
+	self assert: intersections isNotEmpty.
+	self assert: (intersections first asPoint closeTo: 0@0).
+
+	"horizontal line "
+	line := GLine through: 10@20 and: 20@10.
+	intersections := self sortedIntersectionsBetween: shape and: line.
+	self assert: intersections isEmpty.
+
+	"vertical line"
+	"intersectionsWithVerticalLine: 
+	does not work with an empty ellipse"
+	shape := GEllipse center: 0@0 vertex: 9@0 coVertex: 0@9.
+	line := GLine through: 10@10 and: 10@20.
+	intersections := self sortedIntersectionsBetween: shape and: line.
+	self assert: intersections isEmpty.
+]
+
 { #category : #tests }
 GEllipseTest >> testEncompassingRectangle [
 	ellipse := GEllipse center: 4 , -1 vertex: 9 , -1 coVertex: 4 , 2.
@@ -210,6 +240,17 @@ GEllipseTest >> testMinorAxis [
 	self assert: ellipse minorAxis equals: (GSegment with: 10 , 8 with: 10 , 12)
 ]
 
+{ #category : #tests }
+GEllipseTest >> testNonEmpty [
+	| shape line intersections |
+	shape := GEllipse center: 0@0 vertex: 0@10 coVertex: 5@10.
+	line := GLine through: shape center and: 10@10.
+	intersections := self sortedIntersectionsBetween: shape and: line.
+	self assert: intersections isNotEmpty.
+	self assert: (intersections first asPoint closeTo: -7.4535599249993@ -7.4535599249993).
+	self assert: (intersections second asPoint closeTo: 7.4535599249993@ 7.4535599249993).
+]
+
 { #category : #tests }
 GEllipseTest >> testPerimeter [
 	ellipse := GEllipse center: 2,6 vertex: 7, 6 coVertex: 2,9.

src/Geometry/GEllipse.class.st

@@ -144,7 +144,6 @@ GEllipse >> intersectionsWithLine: aGLine [
 	a := self semiMajorAxisLength.
 	b := self semiMinorAxisLength.
 
-	(a = b and: [ a = 0 ]) ifTrue: [ ^ {center} asSet ].
 	m := aGLine a / aGLine b negated.
 	c := aGLine c / aGLine b negated.
 	e := c - k.
@@ -160,6 +159,7 @@ GEllipse >> intersectionsWithLine: aGLine [
 	tk := t * k.
 	sqrtContent := (a2m2 + b2 - t2 - k2 + (2 * tk)).
 	sqrtContent >= 0 ifFalse: [ ^ {  } ]. "No intersections"
+	(a = b and: [ a = 0 ]) ifTrue: [ ^ Set with: center ].
 	sqrt := (a2m2 + b2 - t2 - k2 + (2 * tk)) sqrt.
 	x1 := (h * b2 - (m * a2 * e) + (ab * sqrt)) / (a2m2 + b2).
 	x2 := (h * b2 - (m * a2 * e) - (ab * sqrt)) / (a2m2 + b2).