Similar to the parksim in the R probability book, but 10 times faster

parksim.jl

using Distributions 
# Fast, but too compact 
function parksim_fast(nreps)
    gd=Geometric(0.15)
    mean(begin x=rand(gd)+1; x<=10? 11-x:x-11 end for i=1:nreps)
end
        
# A litte longe but clearer         
function parksim_fast2(nreps)
  gd=Geometric(0.15)
  function f()
     x=rand(gd)+1
     x<=10? 11-x:x-11
  end 
  mean(f() for i=1:nreps)
end

# R like function                 
function parksim(nreps)
    gd=Geometric(0.15)
    nval=rand(gd,nreps)+1
    dvals=map(x->x<=10? 11-x:x-11,nval)
    mean(dvals)
 end
                
# Testing the times 
# Warm up 
parksim_fast2(10)
parksim_fast(10)
parksim(10)

@time parksim_fast2(1000_000_00)
@time parksim_fast(1000_000_00)
@time parksim(1000_000_00)

parksim.R

parksim <-function(nreps) {
 nvals<-rgeom(nreps,0.15)+1
 dvals<-ifelse(nvals<=10,11-nvals,nvals-11)
 mean(dvals)
}

system.time(parksim(100000000))