using Stochy, DataStructures, Gadfly, Stochy.GadflySupport
posterior = @pp pmcmc(50,100) do
local faircoin = flip(0.999) # Prior.
local coin = () -> flip(faircoin ? 0.5 : 0.95) ? :head : :tail
local flips = repeat(coin, 5)
factor(flips == repeat(() ->:head, 5) ? 0 : -Inf)
faircoin
end;
bar(posterior)