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

martin martin.drautzburg at web.de
Thu Oct 29 18:30:09 UTC 2015

```I understand that with (x,y,z)->Bool there is not much I can do other than brute force. But I am not forced to use this
representation. The only thing I'd rather not do, is enumerate all the points.

I thought the reactive guys found ways to manipulate Time->a functions without having to enumerate all the possible
(Time,a) occurrences. But there live is "easy", because the possible times only depend on the start time and the
sampling frequency (I may be awfully mistaken here).

I thought about doing similar things, but with more than one coordinate, i.e. Time and Space. With just one coordinate I
can answer "what will be at Time=t", but with two coordinates, the answer will be a function of space. But I can also
ask "what will be at position x" and the result will be a function of time. Now, that does not look too difficult. I can
always convert (x,y,z)->Bool to (y,z)->Bool if I happen to know x.

I looks like I have to work on step one of the Fenyman Problem Solution Method ("write down the problem").

Thanks again.

Am 10/29/2015 um 10:01 AM schrieb martin:
> 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?
>
> _______________________________________________