On 01/05/16 13:23, Alice Wonder wrote: > On 05/01/2016 05:10 AM, Alice Wonder wrote: >> >> I think this is my autism coming in to play, I think what is very clear >> to me I just am not able to adequately communicate because clearly >> people are not even remotely grasping what I am trying to convey. >> > > Basically whether it is a white list or a black list doesn't matter. > > One is just the complement set of the other. > > It's the set I'm after. Or its complement. I don't care. Not whether my > code should use set A or its complement. > See Gordon's previous answer above: That is, [A-Za-z0-9._][A-Za-z0-9._-] In other words, allowable characters are A-Za-z (upper and lower case), 0-9 (numerics), . and _ (period and underscore). Hyphens are allowed, but NOT as the first character, so maybe easier to just not allow hyphens in your account usernames.