Line circle intersection: Difference between revisions

=={{header|Visual Basic .NET}}==

{{trans|C#}}

<lang vbnet>Module Module1

Structure Point

Implements IComparable(Of Point)

Public Sub New(mx As Double, my As Double)

X = mx

Y = my

End Sub

Public ReadOnly Property X As Double

Public ReadOnly Property Y As Double

Public Function CompareTo(other As Point) As Integer Implements IComparable(Of Point).CompareTo

Dim c = X.CompareTo(other.X)

If c <> 0 Then

Return c

End If

Return Y.CompareTo(other.Y)

End Function

Public Overrides Function ToString() As String

Return String.Format("({0}, {1})", X, Y)

End Function

End Structure

Structure Line

Public Sub New(mp1 As Point, mp2 As Point, Optional segment As Boolean = False)

If P2.CompareTo(P1) < 0 Then

P1 = mp2

P2 = mp1

Else

P1 = mp1

P2 = mp2

End If

IsSegment = segment

If P1.X = P2.X Then

Slope = Double.PositiveInfinity

YIntercept = Double.NaN

Else

Slope = (P2.Y - P1.Y) / (P2.X - P1.X)

YIntercept = P2.Y - Slope * P2.X

End If

End Sub

Public ReadOnly Property P1 As Point

Public ReadOnly Property P2 As Point

Public ReadOnly Property Slope As Double

Public ReadOnly Property YIntercept As Double

Public ReadOnly Property IsSegment As Boolean

Public Function IsVertical() As Boolean

Return P1.X = P2.X

End Function

Public Overrides Function ToString() As String

Return String.Format("[{0}, {1}]", P1, P2)

End Function

End Structure

Structure Circle

Public Sub New(c As Point, r As Double)

Center = c

Radius = r

End Sub

Public ReadOnly Property Center As Point

Public ReadOnly Property Radius As Double

Public Function X() As Double

Return Center.X

End Function

Public Function Y() As Double

Return Center.Y

End Function

Public Overrides Function ToString() As String

Return String.Format("{{ C:{0}, R:{1} }}", Center, Radius)

End Function

End Structure

Function Intersection(oc As Circle, ol As Line) As IEnumerable(Of Point)

Dim LineIntersection = Iterator Function(ic As Circle, il As Line) As IEnumerable(Of Point)

Dim m = il.Slope

Dim c = il.YIntercept

Dim p = ic.X

Dim q = ic.Y

Dim r = ic.Radius

If il.IsVertical Then

Dim x = il.P1.X

Dim B = -2 * q

Dim CC = p * p + q * q - r * r + x * x - 2 * p * x

Dim D = B * B - 4 * CC

If D = 0 Then

Yield New Point(x, -q)

ElseIf D > 0 Then

D = Math.Sqrt(D)

Yield New Point(x, (-B - D) / 2)

Yield New Point(x, (-B + D) / 2)

End If

Else

Dim A = m * m + 1

Dim B = 2 * (m * c - m * q - p)

Dim CC = p * p + q * q - r * r + c * c - 2 * c * q

Dim D = B * B - 4 * A * CC

If D = 0 Then

Dim x = -B / (2 * A)

Dim y = m * x + c

Yield New Point(x, y)

ElseIf D > 0 Then

D = Math.Sqrt(D)

Dim x = (-B - D) / (2 * A)

Dim y = m * x + c

Yield New Point(x, y)

x = (-B + D) / (2 * A)

y = m * x + c

Yield New Point(x, y)

End If

End If

End Function

Dim int = LineIntersection(oc, ol)

If ol.IsSegment Then

Return int.Where(Function(p) p.CompareTo(ol.P1) >= 0 AndAlso p.CompareTo(ol.P2) <= 0)

Else

Return int

End If

End Function

Sub Print(c As Circle, lines() As Line)

Console.WriteLine("Circle: {0}", c)

For Each line In lines

Console.Write(vbTab)

If line.IsSegment Then

Console.Write("Segment: ")

Else

Console.Write("Line: ")

End If

Console.WriteLine(line)

Dim points = Intersection(c, line).ToList

Console.Write(vbTab + vbTab)

If points.Count = 0 Then

Console.WriteLine("do not intersect")

Else

Console.WriteLine("intersect at {0}", String.Join(" and ", points))

End If

Next

Console.WriteLine()

End Sub

Sub Main()

Dim c = New Circle(New Point(3, -5), 3)

Dim lines() As Line = {

New Line(New Point(-10, 11), New Point(10, -9)),

New Line(New Point(-10, 11), New Point(-11, 12), True),

New Line(New Point(3, -2), New Point(7, -2))

}

Print(c, lines)

c = New Circle(New Point(0, 0), 4)

lines = {

New Line(New Point(0, -3), New Point(0, 6)),

New Line(New Point(0, -3), New Point(0, 6), True)

}

Print(c, lines)

c = New Circle(New Point(4, 2), 5)

lines = {

New Line(New Point(6, 3), New Point(10, 7)),

New Line(New Point(7, 4), New Point(11, 8), True)

}

Print(c, lines)

End Sub

End Module</lang>

{{out}}

<pre>Circle: { C:(3, -5), R:3 }

Line: [(-10, 11), (10, -9)]

intersect at (3, -2) and (6, -5)

Segment: [(-10, 11), (-11, 12)]

do not intersect

Line: [(3, -2), (7, -2)]

intersect at (3, -2)

Circle: { C:(0, 0), R:4 }

Line: [(0, -3), (0, 6)]

intersect at (0, -4) and (0, 4)

Segment: [(0, -3), (0, 6)]

intersect at (0, 4)

Circle: { C:(4, 2), R:5 }

Line: [(6, 3), (10, 7)]

intersect at (1, -2) and (8, 5)

Segment: [(7, 4), (11, 8)]

intersect at (8, 5)</pre>