# [Haskell-cafe] Find a point inside (x,y,z) -> Bool

Atze van der Ploeg atzeus at gmail.com
Thu Oct 29 09:23:35 UTC 2015

```This representation ((x,y,z) _> bool) makes it very hard to find a point
inside. Basically it does not give you any info: does the shape have area?
What is it bounding box? Is it convex? Supposing x y and z are rationals
(arbitrary precision), then all these questions are not computable. I
suggest you use a different representation, such as a list of points for a
polygon.
On Oct 29, 2015 10:13 AM, "Jonas Scholl" <anselm.scholl at tu-harburg.de>
wrote:

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> You could try to use a data structure like a kd-tree, which can find the
> nearest neighbours to your point quite efficient.
>
> On 10/29/2015 10:01 AM, martin wrote:
> > Hello all, > > I hope this is not a too silly question. It goes like
> this: > >
> Suppose I have a shape defined as > > (x,y,z) -> Bool > > how can I find
> a Point inside this shape? Obviously I could iterate through all
> possible x,y and z, but this appears > very expensive. > > There may be
> no point at all at x=0. With brute force iteration I would have no clue
> that the False I am receiving with > (0,1,1) is caused by x=0 and I may
> nedlessly try all combinations of y and z without ever receiving a True.
> > > Are there any alternative ways of finding points inside a shape? > >
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