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plurals

POEquals and hashcode for vertices
primarykey
Id
17593282
data
AcceptedAnswerId
17599280
AnswerCount
2
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2013-07-11T12:22:31.093
FavoriteCount
0
LastActivityDate
2013-07-11T17:05:23.360
LastEditDate
2013-07-11T13:23:22.797
LastEditorUserId
12048
OwnerUserId
1926615
ParentId
0
PostTypeId
1
Score
1
ViewCount
208
LastEditorDisplayName
text
Body
I have a couple of vertices which I want to put into a Hashtable. Vertices which are really close to each other are considered as the same vertex. My C# vertex class looks like this: <pre><code>public class Vertex3D { protected double _x, _y, _z; public static readonly double EPSILON = 1e-10; public virtual double x { get { return _x;} set { _x = value; } } public virtual double y { get { return _y; } set { _y = value; } } public virtual double z { get { return _z; } set { _z = value; } } public Vertex3D(double p1, double p2, double p3) { this._x = p1; this._y = p2; this._z = p3; } public override bool Equals(object obj) { var other = obj as Vertex3D; if (other == null) { return false; } double diffx = this.x - other.x; double diffy = this.y - other.y; double diffz = this.z - other.z; bool eqx = diffx > -EPSILON && diffx < EPSILON; bool eqy = diffy > -EPSILON && diffy < EPSILON; bool eqz = diffz > -EPSILON && diffz < EPSILON; return eqx && eqy && eqz; } public override int GetHashCode() { return this.x.GetHashCode() ^ this.y.GetHashCode() ^ this.z.GetHashCode(); } public override string ToString() { return "Vertex:" + " " + x + " " + y + " " + z; } </code></pre> Now lets say I put the following two vertices into a dictionary (a dictionary is a hashtable which doesn't allow null keys): <pre><code> Dictionary<Vertex3D, Vertex3D> vertexList = new Dictionary<Vertex3D, Vertex3D>(); Vertex3D v0 = new Vertex3D(0.000000000000000037842417475065449, -1, 0.00000000000000011646698526992202)); Vertex3D v1 = new Vertex3D(0, -1, 0)); vertexList.Add(v0, v0); vertexList.Add(v1, v1); </code></pre> The problem is that my implementation of equals and hashcode is faulty. The above two vertices are considered as equal because the distance to each other is smaller than EPSILON. BUT they don't return the same hashcode. How do I implement equals and hashcode correctly?
Tags
<c#><hash><geometry><equals><hashcode>
Title
Equals and hashcode for vertices
singulars
PostAcceptedAnswerId
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
PostParentId
1. This table or related slice is empty.
PostTypePostTypeId
1. PTQuestion
UserLastEditorUserId
1. USfinnw
UserOwnerUserId
1. USNMO
plurals
PostLinksPostIdRelatedPostId
1. This table or related slice is empty.
PostLinksRelatedPostIdPostId
1. This table or related slice is empty.
PostsAcceptedAnswerId
1. This table or related slice is empty.
PostsParentIdCreationDate
1. PO
 singulars
 PostTypePostTypeId
 PTAnswer
2. PO
 singulars
 PostTypePostTypeId
 PTAnswer
VotesPostIdCreationDate
1. VO
 singulars
 PostPostId
 POEquals and hashcode for vertices
 UserUserId
 This table or related slice is empty.
 VoteTypeVoteTypeId
 VTUpMod
CommentsPostId
1. This table or related slice is empty.

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