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Imagine the following scenario at the draw of the Lottery: As soon as the ball leaves the lottery drum, the lottery girl announces:

'...the forth Number is... STOP. Ladies and Gentlemen, I need to check first whether the forth number is identical with the first, second or third number. If so, I need to put it back in the lottery drum.'

A funny thought but never heard of in real life so far. Obviously there must be a solution to this problem which manages completely without checks and ensures that no duplicates are drawn. Life rules this out by removing the drawn number from the lottery drum. Just like this we want to handle this problem in our program:

• Loading of the number table (49 elements) with values from 1 to 49
• The randomiser picks the table element, not it's content (1 to number of existing elements)
• The result of the draw is read out of the selected table element
• The table element is deleted (only possible with dynamic tables) and the table shrinks

/* REXX
*/
arg anz
do while anz < 6 ! anz > 12
   say 'Anzahl zu ziehender Zahlen (6 bis 12):'
   pull anz
end
say
say center("Lotto" anz "aus 49",79,'-')
say
kugeln=""
do idx=1 to 49
   kugeln=kugeln" "idx
end
do idx=1 to anz
   rnd=random(1,words(kugeln))
   var.idx=word(kugeln,rnd)
   kugeln=delword(kugeln,rnd,1)
end
zahlausg=""
do x=1 to 49  /* Sortierte Zahlenausgabe */
   do y=1 to anz
      if x=var.y then zahlausg=zahlausg" "var.y
   end
end
say center(zahlausg,79)
say
say center('Viel Erfolg',79,'-')
exit