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(- Demo Tape for 'Peh'; produces the largest primorial that fits in Width.  -)
(-                                                                          -)
(- (C) 2019 Stanislav Datskovskiy ( www.loper-os.org )                      -)
(- http://wot.deedbot.org/17215D118B7239507FAFED98B98228A001ABFFC7.html     -)
(-                                                                          -)
(- You do not have, nor can you ever acquire the right to use, copy or      -)
(- distribute this software ; Should you use this software for any purpose, -)
(- or copy and distribute it to anyone or in any manner, you are breaking   -)
(- the laws of whatever soi-disant jurisdiction, and you promise to         -)
(- continue doing so for the indefinite future. In any case, please         -)
(- always : read and understand any software ; verify any PGP signatures    -)
(- that you use - for any purpose.                                          -)
(-                                                                          -)
(- See also http://trilema.com/2015/a-new-software-licensing-paradigm .     -)
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(------------------------------ Main Program : ------------------------------)

( p is the 'primorial accumulator', and q is the current 'potential prime'. )

( p is initialized to the product of the first two primes, 2 and 3 : )
.6 $p

( q is initialized to 5, i.e. the first prime that is not 2 or 3 :)
.5 $q

( Begin a loop: )
:

        ( Determine GCD(p, q) : )
        p q G

        ( If GCD(p, q) WAS equal to 1, we know that q is a new prime : )
        .1 = 
        {
                ( Find the product pq.
                  The UPPER FZ of this product will land on top of stack,
                  and the LOWER FZ will lie immediately under it : )
                p q *
                
                ( If the UPPER FZ of the product pq was NOT equal to 0...
                  ... then we have overflowed our Width, and must stop: )
                {
                        ( Drop the LOWER FZ of the product pq, because
                          we have overflowed Width and cannot use it : )
                        _

                        ( Leave a 0 on the stack, to trigger termination : )
                        .0

                        ( At this point, we have the largest primorial
                          that can fit in our FZ Width, and we are done. )
                }
                
                ( If the UPPER FZ of the product pq WAS equal to 0...
                  ... then we have NOT overflowed our Width, and continue: )
                {
                        ( Store the LOWER FZ of the product pq to p :)
                        $p

                        ( Leave a 1 on the stack, to trigger continuation : )
                        .1

                        ( At this point, pq is the primorial up to and
                          inclusive of q, and we keep going. )
                }_
        }

        ( If GCD(p, q) WAS NOT equal to 1, we know that q is NOT a prime : )
        {
                ( Leave a 1 on the stack, to signal continuation : )
                .1
        }_

        
        ( After either of the above cases, we must:
          q := q + 2,
          given as any possible next prime after the current q must be odd : )
        q .2 + $q

( If we have a 1, cycle the loop; otherwise, we have the Primorial, in p,
  and must output it and terminate the Tape : )
,

( Emit a Peh Tape which defines the constant 'Primorial' : )
[@Primorial@ ( Regs : none )
.]
p#
[;
]

( Now, terminate with a 'Yes' Verdict, as we have succeeded : )
QY

(--------------------------------~~The End~~---------------------------------)