Yes, the syntax (prob,i,repeat) -> remake(prob,p=rand(Float32,3).*p) defines an anonymous function which takes three parameters, prob, i and repeat and uses only the first one of the three. The anonymous function is then bound to the name prob_func and you may as well have defined it directly as prob_func(prob,i,repeat) = remake(prob,p=rand(Float32,3).*p).