random.hs

randomInUnitSphere :: State StdGen (V3 Double)
randomInUnitSphere = iterateWhile (\v -> norm v ^ 2 >= 1) random'

random' :: Random a => State StdGen a
random' = state random

-- Error 
-- /home/dima/projects/raytracing/src/Main.hs:100:59-65: error:
--    • No instance for (Random (V3 Double))
--        arising from a use of ‘random'’
--    • In the second argument of ‘iterateWhile’, namely ‘random'’
--      In the expression: iterateWhile (\ v -> norm v ^ 2 >= 1) random'
--      In an equation for ‘randomInUnitSphere’:
--          randomInUnitSphere = iterateWhile (\ v -> norm v ^ 2 >= 1) random'