Manually simulate prop_partition

manual.hs

-- Fill in the a, b, ps values from the quickhull-test failure message for the
-- 'partition' test below. Then start `cabal repl` and copy-paste this whole
-- thing in there. The output of the last command is what your 'partition' does
-- on this input.

import Data.Array.Accelerate.Interpreter

-- paste the printed values of a, b and ps here
a = (-454, -137)
b = (-286, -641)
ps = [(-398, -69), (-376, -135)]

let leftOf ((x1, y1), (x2, y2)) (x, y) = let nx = y1 - y2 ; ny = x2 - x1 in nx * x + ny * y P.> nx * x1 + ny * y1
let p1     = P.min a b
let p2     = P.max a b
let us     = Data.List.nub $ Data.List.sort $ P.filter (leftOf (p1,p2)) ps
let vs     = Data.List.nub $ Data.List.sort $ P.filter (leftOf (p2,p1)) ps
let nus    = P.length us
let nvs    = P.length vs
let n      = nus + nvs + 3
let flags  = True : P.replicate nus False P.++ [True] P.++ P.replicate nvs False P.++ [True]
let points = p1 : us P.++ [p2] P.++ vs P.++ [p1]

runN partition (fromList (Z :. n) flags, fromList (Z :. n) points)