Re: Card game deck but with trumps suit for tarot "divination" Is there a better way than enumerating all cards?

[Petter Fryklund <petter.fryklund@atero.se>]

Den lördag 3 februari 2018 kl. 00:05:23 UTC+1 skrev Randy Brukardt:
> "Robert Eachus" <rieachus@comcast.net> wrote in message 
> news:8c806572-009d-4ba2-a20d-de1209e45ca6@googlegroups.com...
> On Monday, January 29, 2018 at 6:17:01 PM UTC-5, Randy Brukardt wrote:
> ...
> >Why go through sorting the Long_Float values?  If you draw without
> >replacement, you draw from 78 cards, then 77, 76, 75,...4,3,2,1.  There
> >is nothing in Ada's random number generators to guarantee that these 78
> >generators work together to produce random values.  By choosing 78
> >values from the same generator you don't have that problem.
> 
> As previously noted, Ada 2020 has added an additional Random function into 
> Discrete_Random to deal with this problem.
> 
> An alternative approach using current Ada would be to use a fixed 
> Discrete_Random range (0 .. 77), and simply discard any values that identify 
> cards already dealt, just retrying to get a random value. This works well 
> and is properly uniform, but only if you are going to deal part of the deck 
> (say 25%). If you need to deal the whole deck, it can get slow toward the 
> end when most of the values returned from Random have already been dealt. 
> (That's especially bad if you forget to special case the last card to the 
> dealt - you don't need a random choice to figure out which one that is after 
> all of the rest have been dealt.)
> 
> Experience shows that most users don't get this right, as did the discussion 
> on the topic (in which many knowledgeable people suggested approaches which 
> just don't work). I had to fix the Janus/Ada random number generator after 
> that discussion, as it had made one of the mistakes as well.
> 
>                                        Randy.

When I generate bridge deals, I first draw cards for North this way, just drawing another if the card was already taken. Then I draw cards for East and South in the same way. West gets what is left.

Petter