```// ************************************************************************** //
//                                                                            //
//    eses                   eses                                             //
//   eses                     eses                                            //
//  eses    eseses  esesese    eses   Embedded Systems Group                  //
//  ese    ese  ese ese         ese                                           //
//  ese    eseseses eseseses    ese   Department of Computer Science          //
//  eses   eses          ese   eses                                           //
//   eses   eseses  eseseses  eses    University of Kaiserslautern            //
//    eses                   eses                                             //
//                                                                            //
// ************************************************************************** //
// This is the original version of Euclid's algorithm for computing greatest  //
// common divisors of given natural numbers: The core of the algorithm is     //
// the fact that the common divisors of a and b are the common divisors of b  //
// and (a-b):                                                                 //
//  * Divisors(a,b) <= Divisors(b,a-b) holds,                                 //
//    since x*t=a and y*t=b imply a-b = (x-y)*t, so that every common divisor //
//    t of a and b also divides a-b.                                          //
//  * Divisors(b,a-b) <= Divisors(a,b) holds,                                 //
//    since x*t=b and y*t=a-b imply a = (a-b)+b = (y+x)*t, thus every common  //
//    divisor t of b and a-b also divides a.                                  //
// ************************************************************************** //

macro N = 1000;

module EuclidSub(nat{N} ?a,?b,x,event !rdy) {
nat{N} y;
x = a;
y = b;
do {
if(x>=y)
next(x) = x-y;
else
next(y) = y-x;
pause;
} while(x!=0 & y!=0);
if(x==0) next(x) = y;
pause;
emit(rdy);
}
drivenby {
a = 126;
b = 56;
await(rdy);
}
```