Give out points of geometries

[Sov-trotter]

PR for #69
So this overloads the convert_simplex() method to break down a linestring.

ls1=LineString([Point(1, 2), Point(4,5), Point(10, 8), Point(1, 2)])
decompose(Point{2, Int}, ls1)
6-element Array{Point{2,Int64},1}:
 [1, 2]
 [4, 5]
 [4, 5]
 [10, 8]
 [10, 8]
 [1, 2]

The repetition of Points is the only visible issue currently. Expected is:

ls1.points.parent.data
4-element Array{Point{2,Int64},1}:
 [1, 2]
 [4, 5]
 [10, 8]
 [1, 2]

[Sov-trotter]

Now the thing is convert_simplex receives only Line so it's pretty hard to avoid the repetitions in there. We can either introduce a new check_repeat() method in the collect_with_eltype() or maybe overload it for LineString/polygon/other higher geometries specifically?

using Makie
a = lines(decompose(Point{2, Int}, ls1))

b = lines(ls1.points.parent.data)

a==b
false

The only thing is that will it be fast enough when we have a very large linestring and that would also result in a quite large array?

[SimonDanisch]

How about overloading decompose?

[Sov-trotter]

Ah. That's doable. BTW can we use the points.parent.data to return our points? Or use the method in the latest commit and iterate over it to remove the duplicates?

Since currently,

using BenchmarkTools

pts = collect(Point{2, Float64}(x/2, (x+1)/3) for x in 1:10000)
ls = LineString(pts)

@btime decompose(Point{2, Float64}, ls)
  925.390 μs (30012 allocations: 2.98 MiB)

@btime ls.points.parent.data
  123.831 ns (6 allocations: 192 bytes)

[Sov-trotter]

So the new overload is for giving out points of a polygon.
A polygon has two parts, and exterior and interiors. In the latest commit, if there are no interiors, an array of points of exterior is given out, but it interiors are present, the data is given out as:

pol = Polygon(LineString(Point{2, Int}[(5, 1), (3, 3), (4, 8), (1, 2), (5, 1)]), [LineString(Point{2, Int}[(2, 2), (3, 8),(5, 6) , (3, 4), (2, 2)]), LineString(Point{2, Int}[(3, 2), (4, 5),(6, 1) , (1, 4), (3, 2)])])

decompose(Point{2, Int}, pol)
2-element Array{Array{Union{Array, Point},N} where N,1}:
 [[5, 1], [3, 3], [4, 8], [1, 2], [5, 1]]
 [Point{2,Int64}[[2, 2], [3, 8], [5, 6], [3, 4], [2, 2]], Point{2,Int64}[[2, 2], [3, 8], [5, 6], [3, 4], [2, 2]]]

Here the first element contains Array of exterior points and second contains arrays of interior linestrings' points.
Is this nested Array approach better? Or what might be a better way to have interiors spread out?

[Sov-trotter]

@visr @SimonDanisch can you take a look?

[Sov-trotter]

@SimonDanisch Really sorry for pestering you this way, but I'd be nice if you can take a look at this PR and #79 too?