On Thursday, November 28, 2019 10:27 CET, basile@starynkevitch.net wrote: Sorry for the important typo. Corrected below On Wednesday, November 27, 2019 22:31 CET, François Pottier wrote:   Hello, I am using zarith and would like to pick a random integer comprised between 0 and some bound. I would like a function Z.random of type Z.t -> Z.t, but this function seems to be missing, and I am not sure how to program it in an efficient and correct way. Any suggestions would be welcome. Thanks!   I tend to believe that the following idea might be good, but please check with real probability experts. I definitely am not one (but one of my best colleagues is one). Let B be the bound. You take a random number modulus 2*B. Let R be that number You modelize the [0;B[ interval as a ring of numbers. For example if B is 5 : 0 -> 1 -> 2 -> 3 -> 4 -> 0 -> 1 -> .... ad infinitium You memoize the previously given random number N On that ring, you go R steps forward and obtain P. That is your new random number and on the next iteration the N would be that P But check with an expert, I am not one -- Basile Starynkevitch http://starynkevitch.net/Basile