definition of convex
https://en.wikipedia.org/wiki/Supporting_hyperplane
definition convex hull ( https://en.wikipedia.org/wiki/Convex_hull )
https://en.wikipedia.org/wiki/Helly%27s_theorem
https://en.wikipedia.org/wiki/Radon%27s_theorem
https://en.wikipedia.org/wiki/Carath%C3%A9odory%27s_theorem_(convex_hull)
http://www.cs.umd.edu/~mount/754/Lects/754lects.pdf
 Graham's scan
 Convex hull by divide and conquer
 QuickHull
 Gift-Wrapping and Jarvis's March
 Chan's Algorithm
 Linear Programming and Smallest Enclosing Disk
Lower bound for convex hull algorithms: sorting
Average number of points on the convex hull of points uniformly distributed
in a square, in a disk
Maximal size of the convex hull of points on a n x n grid